substantially rework file monitors

Remove all event merging and dispatch logic from GFileMonitor.  The only
implementation of GFileMonitor outside of glib is in gvfs and it already
does these things properly.

Get rid of GLocalDirectoryMonitor.  We will use a single class,
GLocalFileMonitor, for both directory and file monitoring.  This will
prevent every single backend from having to create two objects
separately (eg: ginotifydirectorymonitor.c and ginotifyfilemonitor.c).

Introduce GFileMonitorSource as a thread-safe cross-context dispatch
mechanism.  Put it in GLocalFileMonitor.  All backends will be expected
to dispatch via the source and not touch the GFileMonitor object at all
from the worker thread.

Remove all construct properties from GLocalFileMonitor and remove the
"context" construct property from GFileMonitor.  All backends must now
get the information about what file to monitor from the ->start() call
which is mandatory to implement.

Remove the implementation of rate limiting in GFileMonitor and add an
implementation in GLocalFileMonitor.  gvfs never did anything with this
anyway, but if it wanted to, it would have to implement it for itself.
This was done in order to get the rate_limit field into the
GFileMonitorSource so that it could be safely accessed from the worker
thread.

Expose g_local_file_is_remote() internally for NFS detection.

With the "is_remote" functionality exposed, we can now move all
functions for creating local file monitors to a proper location in
glocalfilemonitor.c

Port the inotify backend to adjust to the changes above.  None of the
other backends are ported yet.  Those will come in future commits.

gio/gioenums.h

@@ -328,9 +328,14 @@ typedef enum {
  *   by file renames (moves) and send a single G_FILE_MONITOR_EVENT_MOVED
  *   event instead (NB: not supported on all backends; the default
  *   behaviour -without specifying this flag- is to send single DELETED
- *   and CREATED events).
+ *   and CREATED events).  Deprecated since 2.44: use
+ *   %G_FILE_MONITOR_WATCH_MOVES instead.
  * @G_FILE_MONITOR_WATCH_HARD_LINKS: Watch for changes to the file made
  *   via another hard link. Since 2.36.
+ * @G_FILE_MONITOR_WATCH_MOVES: Watch for rename operations on a
+ *   monitored directory.  This causes %G_FILE_MONITOR_EVENT_RENAMED,
+ *   %G_FILE_MONITOR_EVENT_MOVED_IN and %G_FILE_MONITOR_EVENT_MOVED_OUT
+ *   events to be emitted when possible.  Since: 2.44.
  *
  * Flags used to set what a #GFileMonitor will watch for.
  */
@@ -338,7 +343,8 @@ typedef enum {
   G_FILE_MONITOR_NONE             = 0,
   G_FILE_MONITOR_WATCH_MOUNTS     = (1 << 0),
   G_FILE_MONITOR_SEND_MOVED       = (1 << 1),
-  G_FILE_MONITOR_WATCH_HARD_LINKS = (1 << 2)
+  G_FILE_MONITOR_WATCH_HARD_LINKS = (1 << 2),
+  G_FILE_MONITOR_WATCH_MOVES      = (1 << 3)
 } GFileMonitorFlags;
 
 
@@ -393,7 +399,17 @@ typedef enum {
  * @G_FILE_MONITOR_EVENT_ATTRIBUTE_CHANGED: a file attribute was changed.
  * @G_FILE_MONITOR_EVENT_PRE_UNMOUNT: the file location will soon be unmounted.
  * @G_FILE_MONITOR_EVENT_UNMOUNTED: the file location was unmounted.
- * @G_FILE_MONITOR_EVENT_MOVED: the file was moved.
+ * @G_FILE_MONITOR_EVENT_MOVED: the file was moved -- only sent if the
+ *   (deprecated) %G_FILE_MONITOR_SEND_MOVED flag is set
+ * @G_FILE_MONITOR_EVENT_RENAMED: the file was renamed within the
+ *   current directory -- only sent if the %G_FILE_MONITOR_WATCH_MOVES
+ *   flag is set.  Since: 2.44.
+ * @G_FILE_MONITOR_EVENT_MOVED_IN: the file was moved into the
+ *   monitored directory from another location -- only sent if the
+ *   %G_FILE_MONITOR_WATCH_MOVES flag is set.  Since: 2.44.
+ * @G_FILE_MONITOR_EVENT_MOVED_OUT: the file was moved out of the
+ *   monitored directory to another location -- only sent if the
+ *   %G_FILE_MONITOR_WATCH_MOVES flag is set.  Since: 2.44
  *
  * Specifies what type of event a monitor event is.
  **/
@@ -405,7 +421,10 @@ typedef enum {
   G_FILE_MONITOR_EVENT_ATTRIBUTE_CHANGED,
   G_FILE_MONITOR_EVENT_PRE_UNMOUNT,
   G_FILE_MONITOR_EVENT_UNMOUNTED,
-  G_FILE_MONITOR_EVENT_MOVED
+  G_FILE_MONITOR_EVENT_MOVED,
+  G_FILE_MONITOR_EVENT_RENAMED,
+  G_FILE_MONITOR_EVENT_MOVED_IN,
+  G_FILE_MONITOR_EVENT_MOVED_OUT
 } GFileMonitorEvent;