pari git http server upgrade

[Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>]

Dear PARI developers,

I have just replaced the dumb git http transport by the smart git http
transport. I hope this will be faster and more reliable.

It should be fully compatible with your repository, as long as you use
git version >= 1.6.6 (i.e. later than January 2010).

If you have an account on pari and use the ssh transport, then of course
there will be no difference.

If you see anything wrong, please tell me.

Cheers,
Bill.