Don't draw anything if width or height is zero. Don't print a warning if

Don't draw anything if width or height is zero. Don't print a warning if

	* gdk/win32/gdkdraw.c (gdk_draw_arc): Don't draw anything if width
 	or height is zero. Don't print a warning if Pie or Arc fails, they
	always fail (?) for very narrow ellipses.

	* gdk/win32/gdkdraw.c (gdk_draw_pixmap): Call InvalidateRgn for
 	the part or the destination window corresponding to source area
 	outside of the source drawable's boundary.

	* gdk/win32/gdkdraw.c (gdk_draw_lines, gdk_draw_polygon): Don't do
 	anything if less than two points.

	* gdk/win32/gdkselection.c (gdk_selection_owner_get): Always
 	return NULL. Gtk cut-and-paste inside a single program works
 	better this way. (It always gets the clipboard contents from
 	Windows, not from its own copy, which is cleared anyway. I can't
 	say I fully understand what happens... Emulating the X selection
 	and property stuff is a bit of a mess.)

	* gdk/win32/gdkevents.c
	* gdk/win32/gdkproperty.c: A bít more verbose logging.

	* gdk/win32/gdkregion.c: Fix some memory leaks (temporary regions
 	that never got deleted). Revamp gdk_region_shrink.

	* gdk/win32/gdkregion.c: Fix memory leak, delete temporary regions
 	after use.

	* gtk/gtk.def: Add some missing entry points.

	* gtk/gtkrc.c: Strip trailing directory separator from pixmap path
 	component.