2 bugs in message_list:

2 bugs in message_list:
- in PHP 4.1.x, the first part of in_array may not be an array. This gives a
  lot of warnings in the message display. Not sure how to fix this, so just adding a
  note to it now.
- initialize $aCol to empty array, not empty string, since it's expected to be
  an array further down.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@9298 7612ce4b-ef26-0410-bec9-ea0150e637f0