[WGL] unifying WGL extensions headers

[Aric Cyr]

First just a quick update on my work converting wined3d from using glx to using
wgl.  I have some (i.e. one :( ) basic dx9 demos working, and am trying to iron
out a bug I can't track down easily since it is crashing in the GL library (in
glDrawArrays) and I don't get a backtrace.  I know the spot it is crashing so I
just have to find out why.  My current guess is that I have some GL context
stuff fubar'd somewhere.

Anyways,  now on to my real reason for this post.  Currently there are a _lot_
of #defines for wgl extensions in dll/opengl32/wgl_ext.c.  These are all
necessary of course, but since they are also becoming necessary for wined3d to
use (due to my glx->wgl port) I though it might be better if we included a real
wglext.h into include/ and use that.  SGI maintains a version of this at
http://oss.sgi.com/projects/ogl-sample/ABI/wglext.h

The advantage of using this is that we get all WGL extensions' function
definitions and constants, and SGI maintains it for us :)

So I'd like to propose a patch (which I have done already if there are no
objections):
  1) add wglext.h from SGI's site to include/
  2) change dlls/opengl32/wgl_ext.c to include wglext.h and remove redundant
#defines
  3) rename (CVS = ich!) dlls/opengl32/wgl_ext.h to dlls/opengl32/wgl_private.h
since that is really what it is and the current name is too close to the
official one IMO.   This file is only used by wgl.c and wgl_ext.c anyways, so
name is not too important other than esthetics.

Comments appreciated!