casa-mp-base

revamp grep port due to 35915ffebe and adjust its dependents

There was a mailing list discussion started here:
https://lists.macports.org/pipermail/macports-dev/2018-June/039101.html

Basically, offering the g_prefix variant introduced in 35915ffebe
could cause problems in other ports that use grep. So, after some
deliberation, the decision was made to revamp the grep port to be like
other GNU ports in that it would install itself as ggrep and add
non-g* symlinks in ${prefix}libexec/gnubin. Other ports which relied
on grep have either had their dependencies removed, which means that
they now rely on /usr/bin/grep, or they were adjusted to work with the
new changes to grep's installation. Many of these ports, though,
actually only use grep during the configure phase and they are able to
detect and use ggrep rather than /usr/bin/grep.