QSqlQuery::exec(delete stmt) should not return false on ODBC Driver if SQL_NO_DATA_FOUND is returned

Currently the ODBC-Driver handles return code SQL_NO_DATA_FOUND like an error (unsuccessful). That is: the QSqlQuery::exec function returns false.
So one can not distinguish between an "error" and "no data found". Since QSqlQuery::exec returns eather 'true' or 'false' one can not resolve more than two states. To be sure that no error occured one would have to first issue a select (wether there is data that needs a delete) and than the delete. That is very inefficient and unnecessary.
So in qsql_odbc.cpp function QODBCResult::exec() should return true if SQL_NO_DATA_FOUND was returned by the SQLExecute().

Also the other db driver like like for instance the native PSQL-Driver return true in the same situation. So the behaviour is currently inconsistent.