The unsignedness of large integer user variables was not being
properly preserved when feeded to prepared statements. This was
happening because the unsigned flags wasn't being updated when
converting the user variable is converted to a parameter.

The solution is to copy the unsigned flag when converting the
user variable to a parameter and take the unsigned flag into
account when converting the integer to a string.


mysql-test/r/binlog.result:
  Add test case result for Bug#33798
mysql-test/r/ps.result:
  Add test case result for Bug#33798
mysql-test/t/binlog.test:
  Add test case for Bug#33798
mysql-test/t/ps.test:
  Add test case for Bug#33798
sql/item.cc:
  Take the unsigned flag into account when converting the
  user variable.