Improvement CORE-4215 : Execution of SET STATISTICS INDEX statement could block or slow execution of concurrent attachments

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/branches/B2_5_Release@58604 65644016-39b1-43b1-bf79-96bc8fe82c15
nightly update

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/branches/B2_5_Release@58605 65644016-39b1-43b1-bf79-96bc8fe82c15