CASAuthentication - Fix for a change in the arguments for phpCAS::setPGTStorageFile()

phpCAS 1.3+ no longer takes a 'format' argument for phpCAS::setPGTStorageFile().
This change allows proxy-ticket storage to work with all versions of phpCAS.
Merge branch 'CASAuth_setPGTStorageFile_fix' into CASAuth_DB_PGT_storage

Conflicts:
	lib/Authentication/CASAuthentication.php

I'm including merging in this fix to the CASAuth_DB_PGT_storage feature branch
since it is a relatively minor fix and automatic merging with this feature
won't work due to the proximity of the changes.