The reason for this is that if we change one unique key and then get a failure on the second, we may not be able to rename the first one back before someone else writes the same key value.  In Maria 2.0, when we keep deleted key values in the tree, this will not be a problem anymore
Fixed typedisable concurrent insert/select for SQLCOM_LOAD as there are problems with concurrent threads during index recreation

KNOWN_BUGS.txt:
  More comments
storage/maria/ha_maria.cc:
  Fixed typo (REPLACE -> INSERT)
  Also disable concurrent insert/select for SQLCOM_LOAD as there are problems with concurrent threads during index recreation
storage/maria/ma_open.c:
  Disable versioning (concurrent writes) if more than one unique key