glut: MinGW portability fixes.

Still, it doesn't run as well as the glut binaries...
diff --git a/src/SConscript b/src/SConscript
index 8e914af..9116e9b 100644
--- a/src/SConscript
+++ b/src/SConscript
@@ -5,4 +5,6 @@
 if 'mesa' in env['statetrackers']:
 	SConscript('mesa/SConscript')
 
+SConscript('glut/glx/SConscript')
+
 SConscript('gallium/winsys/SConscript')