Gsql prepared statements

Audit list
 - [ ] GSQLBackend
 - [ ] SSql
 - [ ] gMySQL
 - [ ] gPgSQL
 - [ ] gSqlite3
 - [ ] gOracle
 - [ ] BIND (dnssec)
 - [ ] mydns
This kind of if is not necessary, delete works on null pointers.

Maybe a delete template to do the boilerplate code:
template< class T > void Delete( T*& pVal )
{
    delete pVal;
    pVal = NULL;
}