changes

日程安排程序（日历功能

Changes since 1.1

* Made the system 'authentication aware'. If you've got some sort of authentication module that causes
  $REMOTE_USER to be set (as all of them do), the only username you can delete/modify/add with is whatever
  you logged in as. Some sort of super-user might be added some day. If you don't have an authentication
  method, you just get to change whatever you like.

* A few usability enhancements. If something goes wrong in the add/modify/delete stage, you're always
  given a button to return to the calendar (no pressing back and getting POST missing messages).

* Bug fixes relating the mysql_select_db function, which was hardcoded to select database 'calendar' before,
  instead of being nice and using $mysql_database.

* Bug fix for some browsers where setting a <td bgcolor=xxx> flag caused the rest of the row to default to that
  colour, resulting in the calendar not greying out past days properly.