[GTK] Deprecate public dispatch_event method in objects implementing EventTarget interface
https://bugs.webkit.org/show_bug.cgi?id=123261

Reviewed by Gustavo Noronha Silva.

The interface function should be used instead.

* bindings/scripts/CodeGeneratorGObject.pm:
(GetFunctionDeprecationInformation): Helper function to return the
version when the function was deprecated and the function
replacing the deprecated one.
(GenerateFunction): Check if the function is deprecated to mark it
as such in the header and API docs.
* bindings/scripts/gobject-generate-headers.pl: Replace the unused
WEBKIT_OBSOLETE_API macro with new macros to mark function as
deprecated, using the glib macros so that we don't need checks for
the platform.
* bindings/scripts/test/GObject/WebKitDOMTestActiveDOMObject.h:
* bindings/scripts/test/GObject/WebKitDOMTestCallback.h:
* bindings/scripts/test/GObject/WebKitDOMTestCustomNamedGetter.h:
* bindings/scripts/test/GObject/WebKitDOMTestEventConstructor.h:
* bindings/scripts/test/GObject/WebKitDOMTestEventTarget.h:
* bindings/scripts/test/GObject/WebKitDOMTestException.h:
* bindings/scripts/test/GObject/WebKitDOMTestInterface.h:
* bindings/scripts/test/GObject/WebKitDOMTestObj.h:
* bindings/scripts/test/GObject/WebKitDOMTestSerializedScriptValueInterface.h:
* bindings/scripts/test/GObject/WebKitDOMTestTypedefs.h:
* bindings/scripts/test/GObject/WebKitDOMattribute.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@158083 268f45cc-cd09-0410-ab3c-d52691b4dbfc