privatemsg 5.x-1.5

DB change: use update.php when upgrading to this version from 5.x-1.3 or older.

New settings option to send a welcome message to new users.
Fixed db upgrade if db_prefix is in use (broken in 5.x-1.4 only).
Removed theme_privatemsg_list.. can theme the privatemsg_list_form instead.

From 1.4:
Add button to preview message before sending.
Use db_next_id instead of auto_increment/serial.
Fix php warning from drupal_mail call.
Integration with userpoints module (2.0 API).
From 1.3:
Fix link in notification email so it works if you are already logged in.