Changes for gcc 4.7.3

It would seem that gccgo in 4.7.3 does things slightly differently to
4.7.0.  Hopefully the new way is the same in 4.8.x, but I haven't
checked yet ...

I think these changes may actually be in 4.7.2, but I'm not 100% sure
...
rst2man doesn't always have the same name

Sometimes it's rst2man, sometimes it's rst2man.py ... how irritating.