gl-renderer: fix build with --disable-egl

Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/src/gl-renderer.h b/src/gl-renderer.h
index d4da567..9e4b220 100644
--- a/src/gl-renderer.h
+++ b/src/gl-renderer.h
@@ -32,6 +32,7 @@
 #else
 
 typedef int EGLint;
+typedef int EGLenum;
 typedef void *EGLDisplay;
 typedef void *EGLSurface;
 typedef intptr_t EGLNativeDisplayType;