[Mondrian] automated enforcement for checkin comment prefixes

[John V. Sichi]

I've added a Perforce trigger to enforce the convention of prefixing 
checkin comments like

	MONDRIAN:  in retrospect, nonemptycrossjoin was a big mistake

If you fail to heed it, you'll get an error like the one below.  If this 
happens to you, fix your comments and then resubmit as instructed.

Submitting change 11138.
Locking 1 files ...
Submit validation failed -- fix problems then use 'p4 submit -c 11138'.
'mondrian_checkin' validation failed: Submit fails:  Mondrian checkin 
comments must be prefixed with MONDRIAN:

If the trigger stops you from doing anything you think should be legal, 
please let me know.  I actually made it a little weaker to avoid getting 
hung up on slight variations--it just looks for the keyword MONDRIAN 
(case sensitive) anywhere in the first line of the checkin comments.

JVS