Compatibility fixes for Centos and Ubuntu.  Fixes 'no authenticators available' message.

Thanks for the helpful mutt setup script with gmail.  I only had one problem - I hit the error 'no authenticators available'.  I made a fix for that.


Fixes the error 'no authenticators available'.  Thanks to http://home.roadrunner.com/~computertaijutsu/mutt.html for the fix.