in private message: also match last names in auto-complete of To-field
There is an issue in the Privatemsg queue with an incomplete patch, privatemsg_realname: Permits to search inside realname field using "LIKE %...%".  You're welcome to help re-roll and test the patch.

The patch is for 6.x-2.x but it could fairly easily be re-written for 7.x-2.x.