Fixed the accidentally broken merge join algorithm.

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@59587 65644016-39b1-43b1-bf79-96bc8fe82c15
Slightly reworked the key processing in the hash join algorithm.

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@59588 65644016-39b1-43b1-bf79-96bc8fe82c15
Fixed CORE-4419: Server crashes while sorting records longer than 128KB.

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@59589 65644016-39b1-43b1-bf79-96bc8fe82c15