fcl-db: sqldb: FSelectable must be set to true by default, to work for TSQLConnections which does not provide information about statement (if there will be resultset) at preparation stage.

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@24795 3ad0048d-3df7-0310-abae-a5850022a9f2