DBDriver::Result::freeResult() is useless

[smradCZ]

I think the method DBDriver::Result::freeResult() should be removed. It calls mysql_free_result but it will be done automatically in class destructor.

In case the method is really wanted, then some things should be updated:

• it should return void instead of magic auto
• it should set resultPtr to nullptr after calling mysql_free_result method to ensure destructor won't freeing memory on same pointer again.

[majcl]

Merged into devel by pull request #101