refs #6089 5.6 inplace alter table
refs #6089 alter table needs to be able to upgrade a shared write lock to an exclusive lock

git-svn-id: file:///svn/mysql.com/mysql-5.5.30@54863 c7de825b-a66e-492c-adef-691d508d4ae1
#14 use copy of alter info for inplace alter