Implement fetching from a packed repository over http/https
using the dumb server support files.
I consider some parts of the logic should be in a separate C
program, but it appears to work with my simple tests. I have
backburnered it for a bit too long for my liking, so let's throw
it out in the open and see what happens.
Signed-off-by: Junio C Hamano <junkio@cox.net>