Fixes bug#17264, for alter table on win32 for successfull operation completion
it is used TL_WRITE(=10) lock instead of TL_WRITE_ALLOW_READ(=6), however here
in innodb handler TL_WRTIE is lifted to TL_WRITE_ALLOW_WRITE, which causes
race condition when several clients do alter table simultaneously.


mysql-test/r/lock_multi.result:
  Test case for bug#17264.
mysql-test/t/lock_multi.test:
  Test case for bug#17264