sql/mysql_priv.h:
  after merge fix
  added charset parameter to check_string_length() function
sql/slave.h:
  after merge fix
  USERNAME_LENGTH const is changed to USERNAME_BYTE_LENGTH
sql/sql_parse.cc:
  after merge fix
  added charset parameter to check_string_length() function
sql/sql_yacc.yy:
  after merge fix
  added charset parameter to check_string_length() function