[Toybox] Grep --color and tests.

[Rob Landley]

I got grep --color checked in, and it seems to be working for me, but I need to
fluff out the test suite. The gnu/dammit version of grep is, of course, insane:

  $ grep -o '' README
  $ grep -o '' grep
  Binary file grep matches

It's THE SAME TEST...

Oh, and "echo | grep -w ''" matches, "echo hello | grep -w ''" does not, and
"echo 'one  two' | grep -w ''" matches again, but only with two spaces. Yeah, I
implemented all that. No, there isn't a -w in posix...

Rob