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.