Cleanup: ensure space after file named in headers

Add blank lines after file references to avoid them being interpreted as
doc-strings the following declarations.

source/blender/windowmanager/wm_draw.h

@@ -28,6 +28,7 @@ struct bContext;
 struct wmWindow;
 
 /* wm_draw.c */
+
 void wm_draw_update(struct bContext *C);
 void wm_draw_region_clear(struct wmWindow *win, struct ARegion *region);
 void wm_draw_region_blend(struct ARegion *region, int view, bool blend);