Additional patch for CORE-3362 : Cursors should ignore changes made by the same statement:
- fixed error when "NOT IN" expression is turned into (better optimized) equivalent expression: 
  new RseBoolNode's lost parentForNode member (required later to [not]set stable cursor savepoint)
- replaced pointer to outer ForNode (parentForNode) by boolean flag (ownSavepoint) - it simplifies cloning of nodes


git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@59289 65644016-39b1-43b1-bf79-96bc8fe82c15