select distinct char(column) fails with utf8
ctype_utf8.result, ctype_utf8.test:
  Adding test case
sql_yacc.yy:
  Adding new syntax.
item_strfunc.h:
  Fixing wrong max_length calculation.
  Also, adding CHAR(x USING charset),
  for easier migrating from 4.1 to 5.0,
  according to Monty's suggestion.