README.win32 Add HAVE_WINTAB. Undefine it if bulding without the Wintab

README.win32 Add HAVE_WINTAB. Undefine it if bulding without the Wintab

	* README.win32
	* config.h.win32: Add HAVE_WINTAB. Undefine it if bulding without
 	the Wintab SDK.

	* gdk/win32/gdkinput.c: Hack some more. Still doesn't quite work
 	OK, but getting closer. Guard against bogus tilt data from Wacom
 	ArtPad II with the 3.40 driver. Add ifdefs for HAVE_WINTAB to
 	enable easier building without Wintab.

	* gdk/win32/gdkinput.h
	* gdk/win32/gdkevents.c
	* gdk/win32/gdkwindow.c: Minor changes related related to above.

	* gdk/win32/gdkvisual.c: Simplify a lot, remove leftovers from X11
 	code. As we have just one visual on Win32, no sense to have it in a
 	table, and no need for the hash table.