[Xlibs] A hack for flashplayer

[Keith Packard]

I've discovered that flash player gets confused when it sees a depth 32 
visual available from the server.  I'm sure this is a bug in that code, 
but there's not exactly a lot we can do about it.

I hacked Xlib to ignore depth 32 visuals when an environment variable
(XLIB_ IGNORE_ARGB32) is set so that I can run mozilla and still see the
fine flash content available on the net.

I'm hoping this won't be a problem for many applications; it's a bit hard 
to understand why flash had this problem (it seems weird to happen upon a 
non-default visual and use it's depth when creating images, but not use it 
for creating windows).

-keith