bug#17494: grep bug report: "GREP_OPTIONS" allows a user to break shell script

[Paul Eggert]

Nadav Har'El wrote:
> So I think it would be best if you drop the GREP_OPTIONS feature
> completely.

I tend to agree.  Hindsight is wonderful of course, but GREP_OPTIONS 
should never have been added, as it's a real minefield.  But how would 
we minimize breakage of existing usage that relies on GREP_OPTIONS?  If 
we removed it, we'd probably need a transition period, and have 
documentation of how to get the old behavior if you want it, etc.