Added auto-correct of field length for enum/set tables for ALTER TABLE
This is becasue of a bug in previous MySQL 4.1 versions where the length for enum/set was set incorrectly after ALTER TABLE


mysql-test/r/rpl_start_stop_slave.result:
  Fixed wrong test
mysql-test/r/type_enum.result:
  Added test for wrong enum/set length after alter table
mysql-test/t/ps.test:
  removed empty line
mysql-test/t/type_enum.test:
  Added test for wrong enum/set length after alter table
sql/field.cc:
  Added auto-correct of field length for enum/set tables.
  This is becasue of a bug in previous MySQL 4.1 versions where the length for enum/set was set incorrectly after ALTER TABLE
sql/item_cmpfunc.cc:
  Simple optimization
sql/mysql_priv.h:
  Made local function global
sql/set_var.cc:
  Simple cleanup
sql/sql_table.cc:
  Simple cleanups & optimizations