Fix a code bug

In [xgmthrid.c](https://github.com/dinhviethoa/libetpan/blob/master/src/low-level/imap/xgmthrid.c#L82), `MAILIMAP_EXTENDED_PARSER_MAILBOX_DATA` should be `MAILIMAP_EXTENDED_PARSER_FETCH_DATA`, like [xgmmsgid.c](https://github.com/dinhviethoa/libetpan/blob/master/src/low-level/imap/xgmmsgid.c#L82).