scripts: Add a script to check for bug URLs in the git log

Basic idea of this script is to check the git log for URLs
to the QEMU bugtracker at launchpad.net and to figure out
whether the related bug has been marked there as "Fix released"
(i.e. closed) already. So this script can e.g. be used after
each public release of QEMU to check whether there are any
bug tickets that could be moved from "Fix committed" (or another
state if the author of the patch forgot to update the bug ticket)
to "Fix released".

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1474486942-18754-1-git-send-email-thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>