Garbage returned if result set contains > 0xFFFF columns

This bug affects all versions and was found by Markus Makela.

While text protocol uses length encoded int value for number of columns in a resultset, binary protocol uses a fixed 2 byte length (maximum 65535 columns).
When executing a statement with 65540 columns (0xFFFF+5), the server returns no error, but returns column_count=5, followed by metadata (containing 65540 field descriptions)