CORE-4437: Add support for the RETURNING clause to Embedded SQL.
CORE-4438: Add support for UPDATE OR INSERT statement to Embedded SQL.
Only C/C++ language support is added, other languages will be supported in trunk.

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/branches/B2_5_Release@59632 65644016-39b1-43b1-bf79-96bc8fe82c15
Updated the docs.

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/branches/B2_5_Release@59636 65644016-39b1-43b1-bf79-96bc8fe82c15