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.
4d35ca86f3