Revert usage warning to an error

src/lua_script.c

@@ -441,7 +441,7 @@ int LUA_CheckGlobals(lua_State *L, const char *word)
 		const char *str = luaL_checklstring(L, 2, &strlength);
 
 		if (strlength > 6)
-			LUA_UsageWarning(L, "mapmusname: Music name too long - truncated to six characters.");
+			return luaL_error(L, "string length out of range (maximum 6 characters)");
 
 		if (strlen(str) < strlength)
 			return luaL_error(L, "string must not contain embedded zeros!");