The value of the actual argument of BIT-type-arg stored procedure was binlogged as non-escaped
sequence of bytes corresponding to internal representation of the bit value.

The patch enforces binlogging of the bit-argument as a valid literal: prefixing the quoted bytes
sequence with _binary.
Note, that behaviour of Item_field::var_str for field_type() of MYSQL_TYPE_BIT is exceptional
in that the returned string contains the binary representation even though result_type() of
the item is INT_RESULT.