sql/item_func.cc:
  change according new structure of udf_func
sql/sql_parse.cc:
  change according with new structure of udf_func
sql/sql_udf.cc:
  change parameter of mysql_drop_func and add_func
sql/sql_udf.h:
  change type of name from *char to LEX_STRING, delete name_length
sql/sql_yacc.yy:
  change according with new structure of udf_func