docs: Fix links to symbols outside the allowed namsepace

Use markdown links for anything that the docs don't depend upon,
like gtk, pixbuf, etc

gio/gapplicationcommandline.c

@@ -55,7 +55,7 @@
  * commandline to this process).
  *
  * The `GApplicationCommandLine` object can provide the @argc and @argv
- * parameters for use with the [struct@Glib.OptionContext] command-line parsing API,
+ * parameters for use with the [struct@GLib.OptionContext] command-line parsing API,
  * with the [method@Gio.ApplicationCommandLine.get_arguments] function. See
  * [gapplication-example-cmdline3.c][gapplication-example-cmdline3]
  * for an example.

gio/gdatagrambased.c

@@ -62,7 +62,7 @@
  * `G_IO_ERROR_TIMED_OUT` if no progress was made. To know when a call would
  * successfully run you can call [method@Gio.DatagramBased.condition_check] or
  * [method@Gio.DatagramBased.condition_wait]. You can also use
- * [method@Gio.DatagramBased.create_source] and attach it to a [struct@Glib.MainContext]
+ * [method@Gio.DatagramBased.create_source] and attach it to a [struct@GLib.MainContext]
  * to get callbacks when I/O is possible.
  *
  * When running a non-blocking operation applications should always be able to

gio/gfileinputstream.c

@@ -42,8 +42,8 @@
  * stream to jump to arbitrary positions in the file, provided the 
  * filesystem of the file allows it. To find the position of a file
  * input stream, use [method@Gio.Seekable.tell]. To find out if a file input
- * stream supports seeking, use [iface@Gio.Seekable.can_seek].
- * To position a file input stream, use [iface@Gio.Seekable.seek].
+ * stream supports seeking, use [vfunc@Gio.Seekable.can_seek].
+ * To position a file input stream, use [vfunc@Gio.Seekable.seek].
  **/
 
 static void       g_file_input_stream_seekable_iface_init    (GSeekableIface       *iface);

gio/gicon.c

@@ -63,7 +63,7 @@
  * be prepared to handle at least the three following cases:
  * [iface@Gio.LoadableIcon], [class@Gio.ThemedIcon] and [class@Gio.EmblemedIcon].
  * It may also make sense to have fast-paths for other cases (like handling
- * [class@GdkPixbuf.Pixbuf] directly, for example) but all compliant `GIcon`
+ * [GdkPixbuf](https://docs.gtk.org/gdk-pixbuf/class.Pixbuf.html) directly, for example) but all compliant `GIcon`
  * implementations outside of GIO must implement [iface@Gio.LoadableIcon].
  *
  * If your application or library provides one or more `GIcon`

gio/gmenumodel.c

@@ -103,7 +103,7 @@
  * identifies an action in an action group. Which action group(s) provide
  * actions depends on the context in which the menu model is used.
  * E.g. when the model is exported as the application menu of a
- * [class@Gtk.Application], actions can be application-wide or window-specific
+ * [GtkApplication](https://docs.gtk.org/gtk4/class.Application.html), actions can be application-wide or window-specific
  * (and thus come from two different action groups). By convention, the
  * application-wide actions have names that start with `app.`, while the
  * names of window-specific actions start with `win.`.

gio/gmountoperation.c

@@ -45,7 +45,7 @@
  *
  * Users should instantiate a subclass of this that implements all the
  * various callbacks to show the required dialogs, such as
- * [class@Gtk.MountOperation]. If no user interaction is desired (for example
+ * [GtkMountOperation](https://docs.gtk.org/gtk4/class.MountOperation.html). If no user interaction is desired (for example
  * when automounting filesystems at login time), usually `NULL` can be
  * passed, see each method taking a `GMountOperation` for details.
  *

gio/gpropertyaction.c

@@ -65,18 +65,18 @@
  * in sync with the property value — its state is the property value.
  *
  * For example, it might be useful to create a [iface@Gio.Action] corresponding
- * to the `visible-child-name` property of a [class@Gtk.Stack] so that the
+ * to the `visible-child-name` property of a [GtkStack](https://docs.gtk.org/gtk4/class.Stack.html) so that the
  * current page can be switched from a menu.  The active radio indication in the
  * menu is then directly determined from the active page of the
- * [class@Gtk.Stack].
+ * `GtkStack`.
  *
  * An anti-example would be binding the `active-id` property on a
- * [class@Gtk.ComboBox].  This is because the state of the combobox itself is
+ * [GtkComboBox](https://docs.gtk.org/gtk4/class.ComboBox.html).  This is because the state of the combo box itself is
  * probably uninteresting and is actually being used to control
  * something else.
  *
  * Another anti-example would be to bind to the `visible-child-name`
- * property of a [class@Gtk.Stack] if this value is actually stored in
+ * property of a [GtkStack](https://docs.gtk.org/gtk4/class.Stack.html) if this value is actually stored in
  * [class@Gio.Settings].  In that case, the real source of the value is
  * [class@Gio.Settings].  If you want a [iface@Gio.Action] to control a setting
  * stored in [class@Gio.Settings], see [method@Gio.Settings.create_action]

gio/gresource.c

@@ -52,7 +52,7 @@ G_DEFINE_BOXED_TYPE (GResource, g_resource, g_resource_ref, g_resource_unref)
  *
  * Applications and libraries often contain binary or textual data that is
  * really part of the application, rather than user data. For instance
- * [class@Gtk.Builder] `.ui` files, splashscreen images, [class@Gio.Menu] markup
+ * [GtkBuilder](https://docs.gtk.org/gtk4/class.Builder.html) `.ui` files, splashscreen images, [class@Gio.Menu] markup
  * XML, CSS files, icons, etc. These are often shipped as files in
  * `$datadir/appname`, or manually included as literal strings in the code.
  *
@@ -82,7 +82,7 @@ G_DEFINE_BOXED_TYPE (GResource, g_resource, g_resource_ref, g_resource_unref)
  *    the preprocessing step is skipped.
  *
  *  - `to-pixdata` (deprecated since gdk-pixbuf 2.32) which will use the
- *    `gdk-pixbuf-pixdata` command to convert images to the [class@Gdk.Pixdata]
+ *    `gdk-pixbuf-pixdata` command to convert images to the [GdkPixdata](https://docs.gtk.org/gdk-pixbuf/class.Pixdata.html)
  *    format, which allows you to create pixbufs directly using the data inside
  *    the resource file, rather than an (uncompressed) copy of it. For this, the
  *    `gdk-pixbuf-pixdata` program must be in the `PATH`, or the
@@ -155,7 +155,7 @@ G_DEFINE_BOXED_TYPE (GResource, g_resource, g_resource_ref, g_resource_unref)
  * also use URIs like `resource:///org/gtk/Example/data/splashscreen.png` with
  * [iface@Gio.File] to access the resource data.
  *
- * Some higher-level APIs, such as [class@Gtk.Application], will automatically
+ * Some higher-level APIs, such as [GtkApplication](https://docs.gtk.org/gtk4/class.Application.html), will automatically
  * load resources from certain well-known paths in the resource namespace as a
  * convenience. See the documentation for those APIs for details.
  *

gio/gsimpleaction.c

@@ -32,8 +32,6 @@
  * A `GSimpleAction` is the obvious simple implementation of the
  * [iface@Gio.Action] interface. This is the easiest way to create an action for
  * purposes of adding it to a [class@Gio.SimpleActionGroup].
- *
- * See also [class@Gtk.Action].
  */
 
 struct _GSimpleAction