Issues #19 and #23

For issue #19:
- create MySQL_Protocol::get_myds()
- create MySQL_Protocol::generate_pkt_row()
- modified MySQL_Session::(*admin_func)(MySQL_Session *) to MySQL_Session::(*admin_func)(MySQL_Session *,ProxySQL_Admin *,PtrSize_t *) so it can access more data
- fixed an invalid strdup in SQLite3_row::add_fields()
- added SQLite3_result::rows_count
- SQLite3DB instances in Standard_ProxySQL_Admin are now public
- create Standard_ProxySQL_Admin::SQLite3_to_MySQL()

For issue #23 :
- added __dump_pkt() in mysql_data_stream.cpp

Bug fix:
Added a missing pthread_mutex_unlock() in Admin/child_mysql()

Minor clean-ups