Fix: Don't rely on static initialization to set up sprite font caches.

The order of static initialization is undefined, so this can cause initalization
before relevant caches are initializations.

(cherry picked from commit f454ec8d63)

src/fontcache.h

@@ -37,6 +37,8 @@ public:
 	FontCache(FontSize fs);
 	virtual ~FontCache();
 
+	static void InitializeFontCaches();
+
 	static int GetDefaultFontHeight(FontSize fs);
 
 	/**