Fix C++ build.

Makefile.win

@@ -184,6 +184,8 @@ clean:
 	rm -f audio/xaudio-c/*.o
 	rm -f conf/*.o
 	rm -f gfx/*.o
+	rm -f gfx/context/*.o
+	rm -f gfx/fonts/*.o
 	rm -f gfx/py_state/*.o
 	rm -f record/*.o
 	rm -f input/*.o

gfx/gl.c

@@ -46,6 +46,9 @@
 #include "shader_glsl.h"
 #endif
 
+extern const GLfloat vertexes_flipped[];
+extern const GLfloat white_color[];
+
 // Used for the last pass when rendering to the back buffer.
 const GLfloat vertexes_flipped[] = {
    0, 0,