DROP DATABASE failed because of file ext not in TYPELIB of known extensions.
  General solution - construct a TYPELIB at runtime instead of a static list.


mysql-test/r/ndb_basic.result:
  Bug#6031
    New test for bug
mysql-test/t/ndb_basic.test:
  Bug#6031
    New test for bug
sql/ha_ndbcluster.cc:
  Cosmetic fix
sql/handler.cc:
  Bug#6031
    New function - ha_known_exts()
    We can construct TYPELIB of known db file extensions.
sql/handler.h:
  Bug#6031
    New function - ha_known_exts()
sql/sql_db.cc:
  Bug#6031
    We use a constructed list of known extensions instead of a static list