#ifdef HAVE_purify removed

per-file comments:
  mysql-test/t/partition_not_windows.test
Bug#39102 valgrind build does not compile in realpath, which make DATA/INDEX DIR fail 
    test reenabled

  mysys/my_symlink.c
Bug#39102 valgrind build does not compile in realpath, which make DATA/INDEX DIR fail 
  superfluous ifdef removed, comments fixed