- lifting a limit: INSERT|REPLACE SELECT and LOAD DATA always prevented versioning, now what do so is if
the table is empty.
- lifting another limit: versioning was disabled if table had more than one unique index
- correcting test of statement-based binlogging, when converting read locks to TL_READ_NO_INSERT

KNOWN_BUGS.txt:
  removing mostly fixed limitation (see ha_maria.cc)
mysql-test/r/maria-mvcc.result:
  result update
mysql-test/t/maria-mvcc.test:
  now when table is empty it does not do versioning, so test hung; inserting one row at start of the test,
  to enable versioning.
sql/sql_parse.cc:
  Maria team wrongly removed this "break", thanks Davi for noticing
storage/maria/ha_maria.cc:
  - We used to prevent versioning in INSERT/REPLACE SELECT and LOAD DATA, because the index rebuild done by
  bulk insert sometimes, is unsafe when versioning is on. Here we change that: in store_lock(), if the table is empty
  (which is required for index rebuild to be used), we disable versioning; in start_bulk_insert(), we don't do
  index rebuild if versioning is enabled.
  - Test for statement-based binlogging was incomplete: statement-based binlogging is on for this statement
  if binlog is open and statement has binlogging enabled and statement is not doing row-based binlogging
storage/maria/ma_open.c:
  Monty and I agreed that it's ok to have versioning on a table with more than one unique index: if an INSERT
  hits a duplicate key when inserting the second index' key, no other thread should be able to touch the 
  first index' just-inserted key, because that key has an uncommitted transaction id, so the first thread
  should have time to remove the first index' key.