http: handle push of bundles > 2 GB again (issue3017)
It was very elegant that httpsendfile implemented __len__ like a string. It was
however also dangerous because that protocol can't handle sizes bigger than 2 GB.
Mercurial tried to work around that, but it turned out to be too easy to
introduce new errors in this area.
With this change __len__ is no longer implemented at all and the code will work
the same way for short and long posts.
$ hg init dir
$ cd dir
$ echo bleh > bar
$ hg add bar
$ hg ci -m 'add bar'
$ hg cp bar foo
$ echo >> bar
$ hg ci -m 'cp bar foo; change bar'
$ hg debugrename foo
foo renamed from bar:26d3ca0dfd18e44d796b564e38dd173c9668d3a9
$ hg debugindex bar
rev offset length base linkrev nodeid p1 p2
0 0 6 0 0 26d3ca0dfd18 000000000000 000000000000
1 6 7 1 1 d267bddd54f7 26d3ca0dfd18 000000000000