Unconditionally flush the page cache to disk if FLUSH_ALL / FLUSH_FINI modes are used and FW=OFF. This puts a little bit more consistency and favors explicit flushes over implicit ones (e.g. when database is detached and its file is closed).

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58658 65644016-39b1-43b1-bf79-96bc8fe82c15
Added conditional locking option to Firebird::Sync.

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58659 65644016-39b1-43b1-bf79-96bc8fe82c15