Trying to speed up compilation a bit

panda/src/glxdisplay/glxdisplay_composite1.cxx

@@ -0,0 +1,5 @@
+#include "config_glxdisplay.cxx"
+#include "glxGraphicsBuffer.cxx"
+#include "glxGraphicsPipe.cxx"
+#include "glxGraphicsStateGuardian.cxx"
+#include "glxGraphicsWindow.cxx"