Replace fatal error with graceful skip & useful message on sync users to contacts

per this forum:

http://forum.civicrm.org/index.php/topic,11773.0.html

Patched files (attached) replace ugly fatal error and incomplete sync with semi-useful message and the ability for the sync to complete.

e.g. I have one record screwing up the sync where two joomla IDs are being matched to one civicrm contact. One on the billing e-mail and the other on the primary. This patch allows the sync to continue past that user.

Sorry, am uploading full patched 3.1.3 files not patch as having a few issues. Only one word changed in CMSUser.php

Note that there were actually about 50 users breaking the sync when I started and all but one were resolved by truncating the civicrm_uf_match table and re-syncing. Perhaps there should be a front-end function to sync that table when the sync hits issues?