When make uses 'makedefs -v' to create date.h, force it to create
gitinfo.txt all the time instead of just when that doesn't already
exist. Use 'make GITINFO=0' to get the previous behavior.
To skip it entirely, you need to do that and also make sure that
some file by that name already exists. 'touch dat/gitinfo.txt' or
perhaps 'echo "#no git" > dat/gitinfo.txt' would suffice.
Hide the scary perl command during 'make all' feedback in src/.
I'm not a shell programmer but this works fine for me when skipping
NHgithook::NHversioning because dat/gitinfo.txt is already present,
when creating dat/gitinfo.txt successfully, and when creation fails
because perl can't find NHgithook.pm. It hasn't been tested when
perl itself is absent.
