implementation of mysql_stmt_reset client end

include/mysql.h:
  add mysql_stmt_reset prototype
include/mysql_com.h:
  add COM_STMT_RESET
libmysql/libmysql.def:
  Add mysql_stmt_reset def
sql/sql_prepare.cc:
  Fix selects hang after windows slowdown issue fix (send_fields)
sql/sql_parse.cc:
  Add COM_STMT_RESET
sql/mysql_priv.h:
  add defination of mysql_stmt_reset

include/mysql_com.h

@@ -44,6 +44,7 @@ enum enum_server_command
   COM_TIME, COM_DELAYED_INSERT, COM_CHANGE_USER, COM_BINLOG_DUMP,
   COM_TABLE_DUMP, COM_CONNECT_OUT, COM_REGISTER_SLAVE,
   COM_PREPARE, COM_EXECUTE, COM_LONG_DATA, COM_CLOSE_STMT,
+  COM_RESET_STMT, 
   COM_END				/* Must be last */
 };