Fix pasting large amounts of text in wxGTK.

Fix pasting large amounts of text in wxGTK.

We need to process GDK_PROPERTY_NOTIFY events when yielding for
wxEVT_CATEGORY_CLIPBOARD, otherwise we never receive large selections.

As GDK_PROPERTY_NOTIFY can be also used for non-clipboard stuff, exceptionally
assign 2 categories to it and process it in either case.

Closes #14284.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71439 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775