Replace public MetaFrameGeometry with MetaFrameBorders

There were actually *two* MetaFrameGeometry structs: one in theme-private.h,
one in frame.h. The latter public struct was populated by a mix of (void*)
casting and int pointers, usually pulling directly from the data in the private
struct.

Remove the public struct, replace it with MetaFrameBorders and scrap all
the pointer hacks to populate it, instead relying on both structs being used
in common code.

This commit should be relatively straightforward, and it should not do any
tricky logic at all, just a sophisticated find and replace.

https://bugzilla.gnome.org/show_bug.cgi?id=644930

src/meta/common.h

@@ -25,9 +25,10 @@
 #ifndef META_COMMON_H
 #define META_COMMON_H
 
-/* Don't include GTK or core headers here */
+/* Don't include core headers here */
 #include <X11/Xlib.h>
 #include <glib.h>
+#include <gtk/gtk.h>
 
 typedef struct _MetaResizePopup MetaResizePopup;
 
@@ -302,6 +303,14 @@ struct _MetaButtonLayout
   gboolean right_buttons_has_spacer[MAX_BUTTONS_PER_CORNER];
 };
 
+typedef struct _MetaFrameBorders MetaFrameBorders;
+struct _MetaFrameBorders
+{
+  /* The frame border is made up of two pieces - an inner visible portion
+   * and an outer portion that is invisible but responds to events.
+   */
+  GtkBorder visible;
+};
 /* should investigate changing these to whatever most apps use */
 #define META_ICON_WIDTH 32
 #define META_ICON_HEIGHT 32