cad/gerbv can be helped

[Ash Gokhale]

I got it to build on 12.1  by dropping the broken,deprecated from the
Makefile  and  updating distinfo to the following.
Seems that the upstream made changes without bumping the rev number.
SHA256 (gerbv-2.7.0.tar.gz) =
c5ee808c4230ce6be3ad10ab63c547098386d43022704de25ddb9378e62053b4
SIZE (gerbv-2.7.0.tar.gz) = 569140
...
& make install
===>  Installing for gerbv-2.7.0_1
===>  Checking if gerbv is already installed
===>   Registering installation for gerbv-2.7.0_1
Installing gerbv-2.7.0_1...
I'm willing to be the maintainer as well.