Modified IStatement interface in our API:
1. Never allocate empty statement - always use att->prepare() to create statement interface
2. Separated IStatement into 2 parts - statement itself and resultset.
3. Added stmt->openCursor() (and att->openCursor() for unprepared statements) to create IResultSet.
4. Always use IMessageMetadata (former IParametersMetadata) to pass message fromat info from client,
   therefore avoiding need in BLR generation in client applications.



git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@57663 65644016-39b1-43b1-bf79-96bc8fe82c15