Unsupported grep options

[Jamboretz, Chris]

First let me say thanks for providing this set of tools. Our tools and scripts 
are currently only using gzip and its corresponding zgrep, etc. In trying to 
switch to different compression methods I'm hoping to swap out gzip's zgrep 
with zutil's zgrep and so on. This will allow the existing and legacy scripts 
to continue on as if nothing has changed. These scripts are a huge amount of 
code going back over a decade and used by thousands. Anyway, that's the 
background.

I've found some unsupported command line options and the first three are 
probably the biggest concern:

--silent
-P  --perl-regexp
--colour

others are

-G  --basic-regexp
-U  --binary
-u  --unix-byte-offsets
-T  --initial-tab
-NUM
--line-buffered
--label=LABEL

Thank you,
Chris