GTask: new GAsyncResult implementation / threaded task manager

GTask is a replacement for GSimpleAsyncResult and GIOScheduler, that
also allows for making cancellable wrappers around non-cancellable
functions (as in GThreadedResolver).

https://bugzilla.gnome.org/show_bug.cgi?id=661767

docs/reference/gio/gio-docs.xml

@@ -42,6 +42,7 @@
         <xi:include href="xml/gasyncresult.xml"/>
         <xi:include href="xml/gioscheduler.xml"/>
         <xi:include href="xml/gsimpleasyncresult.xml"/>
+        <xi:include href="xml/gtask.xml"/>
     </chapter>
     <chapter id="conversion">
         <title>Data conversion</title>

docs/reference/gio/gio-sections.txt

@@ -3921,3 +3921,56 @@ g_test_dbus_unset
 g_test_dbus_get_type
 g_test_dbus_flags_get_type
 </SECTION>
+
+<SECTION>
+<FILE>gtask</FILE>
+<TITLE>GTask</TITLE>
+GTask
+g_task_new
+g_task_set_task_data
+g_task_set_priority
+g_task_set_check_cancellable
+g_task_set_return_on_cancel
+g_task_set_source_tag
+<SUBSECTION>
+g_task_report_error
+g_task_report_new_error
+<SUBSECTION>
+g_task_get_task_data
+g_task_get_priority
+g_task_get_cancellable
+g_task_get_check_cancellable
+g_task_get_return_on_cancel
+g_task_get_context
+g_task_get_source_object
+g_task_get_source_tag
+<SUBSECTION>
+g_task_return_boolean
+g_task_return_int
+g_task_return_pointer
+g_task_return_error
+g_task_return_new_error
+g_task_return_error_if_cancelled
+<SUBSECTION>
+g_task_propagate_boolean
+g_task_propagate_int
+g_task_propagate_pointer
+g_task_had_error
+<SUBSECTION>
+g_task_run_in_thread
+g_task_run_in_thread_sync
+GTaskThreadFunc
+g_task_attach_source
+<SUBSECTION>
+g_task_is_valid
+<SUBSECTION Standard>
+GTaskClass
+GTaskPrivate
+G_TYPE_TASK
+G_TASK
+G_IS_TASK
+G_TASK_CLASS
+G_IS_TASK_CLASS
+G_TASK_GET_CLASS
+g_task_get_type
+</SECTION>

docs/reference/gio/gio.types

@@ -135,3 +135,4 @@ g_menu_get_type
 g_menu_item_get_type
 g_test_dbus_get_type
 g_test_dbus_flags_get_type
+g_task_get_type