[Groff] Rewrite of grog

[Bernd Warken]

I rewrote all files of grog.  These are found in <groff-top>/src/roff/grog.

These files didn't have a license, so I added the GPL to all files.
Please check the copyright years and whether James Clark is
the original author.  I could only get as far back as groff-1.10 to check.

Could you please test grog with your roff files.  I could not test
mm files.  But the testing of ms was very weak, too.

A problem occurs if grog tests 2 or more macro packages for a
single file.  This has to be tested.

Bernd Warken