glx/windows: Add wgl.h to the sources list
glx/windows: Add wgl.h to the sources list

Otherwise it won't be picked in the tarball and the build will fail.

Fixes: 533b3530c12 ("direct-to-native-GL for GLX clients on Cygwin
("Windows-DRI")")
Cc: "13.0" <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>
Signed-off-by: Andreas Boll <041cac00e0cb793452cecf5c52a77db13d069cf3@gmail.com>
Reviewed-by: Jon Turney <45846cba2ea093796a8b1c25d70d679d8107179f@dronecode.org.uk>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler