games/maelstrom: Fix build with Clang 6

./load.h:109:22: error: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]

sprintf(path, "%s"DIR_SEP"%s", directory, filename);
                  ^

./load.h:95:16: warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]

directory = LIBDIR;
            ^

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p475044_s336572/logs/maelstrom-3.0.6_13.log

• While here fix some bad implicit declaration warnings