Implement -v (verbose) option for pull methods other than local transport.

This moves the private "say()" function to pull.c, renames it to
"pull_say()", and introduces a global variable "get_verbosely" that
makes the pull backends report what they fetch.  The -v option is
added to git-rpull and git-http-pull to match git-local-pull.

The documentation is updated to describe these pull commands.

Signed-off-by: Junio C Hamano <junkio@cox.net>