fix push --quiet: add 'quiet' capability to receive-pack

fix push --quiet: add 'quiet' capability to receive-pack

Currently, git push --quiet produces some non-error output, e.g.:

 $ git push --quiet
 Unpacking objects: 100% (3/3), done.

This fixes a bug reported for the fedora git package:

 https://bugzilla.redhat.com/show_bug.cgi?id=725593

Reported-by: Jesse Keating <jkeating@redhat.com>
Cc: Todd Zullinger <tmz@pobox.com>
Commit 90a6c7d4 (propagate --quiet to send-pack/receive-pack)
introduced the --quiet option to receive-pack and made send-pack
pass that option. Older versions of receive-pack do not recognize
the option, however, and terminate immediately. The commit was
therefore reverted.

This change instead adds a 'quiet' capability to receive-pack,
which is a backwards compatible.

In addition, this fixes push --quiet via http: A verbosity of 0
means quiet for remote helpers.

Reported-by: Tobias Ulmer <tobiasu@tmux.org>
Signed-off-by: Clemens Buchacher <drizzd@aon.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>