git-shortlog: make the mailmap configurable.
git-shortlog: make the mailmap configurable.

In addition to hardcoded list of kernel people, read from .mailmap file
the list of email-to-name translations.  Modernize regexps here and there
minimally while at it.

Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git