Support UTF8 basic characters on ImageTextEx()

Supported UTF8 range equivalent to [128..255] (80h..FFh)
Exposed and renamed text function GetGlyphIndex()
Renamed spriteFont parameter name to simply font
Small security check on transmission mission ending screen

games/transmission/screens/screen_ending.c

@@ -113,7 +113,7 @@ void InitEndingScreen(void)
             
             strcpy(headline, title);     // Base headline updated
             
-            free(title);
+            if (title != NULL) free(title);
         }
     }