textproc/gnugrep: add missing dependency, build with --program-prefix=gHEADmain

- Add run-time dependency on `textproc/groff': the manual page won't be
  rendered if groff(1) is not installed;
- By popular demand, configure the port with `--program-prefix=g' as we
  do for other GNU utilities.  This places the binaries within the same
  namespace more consistently; several other non-GNU/Linux systems, e.g.
  NetBSD, OpenBSD, Solaris, macOS (Homebrew) are doing the same.  Avoid
  POLA violation by creating traditionally named compatibility symlinks.

PR:	263275, 265729

0 files changed, 0 insertions, 0 deletions