(svn r15910) -Fix [FS#2777]: Clarify that TILE_INVALID is part of AIMap make doxygen output some documentation for it.

src/ai/api/ai_map.hpp

@@ -17,6 +17,9 @@ public:
 		TILE_INVALID = INVALID_TILE, //!< Invalid TileIndex.
 	};
 #endif /* DEFINE_SCRIPT_FILES */
+#ifdef DOXYGEN_SKIP
+	const static TileIndex TILE_INVALID; //!< Invalid TileIndex.
+#endif
 
 	static const char *GetClassName() { return "AIMap"; }