hw/xwin/glx: Rewrite WGL wrappers after Xserver conversion to direct GL dispatch

hw/xwin/glx: Rewrite WGL wrappers after Xserver conversion to direct GL dispatch

v1: Rewrite by Marc Haesen of the WGL wrapper function generation script to use
Khronos group XML.

v2: Remove -dispatchheader option, since dispatch.h doesn't exist anymore, use
the private glapi interface to construct the GL dispatch table for the native
WGL thunks.

v3:
Rewrite to generate shims for the OpenGL 1.2.1 (GL 1.2 + GL_ARB_imaging
+GL_ARB_multitexture + GL_ARB_texture_compression(?)) functions the server links
directly with rather than libGL.

These shims dispatch to either the mesa GL DLL, or a thunking DLL containing
cdecl-to-stcall wrapper functions for the native GL DLL.

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Reviewed-by: Adam Jackson <ajax@redhat.com>