Allow control over the elimination of duplicate email names and addresses

--remove-duplicates will use the first email name or address presented
--noremove-duplicates will emit all names and addresses

--remove-duplicates is enabled by default

For instance:

$ ./scripts/get_maintainer.pl -f drivers/char/tty_ioctl.c
Greg Kroah-Hartman <gregkh@suse.de>
Alan Cox <alan@linux.intel.com>
Mike Frysinger <vapier@gentoo.org>
Alexey Dobriyan <adobriyan@gmail.com>
linux-kernel@vger.kernel.org

$ ./scripts/get_maintainer.pl -f --noremove-duplicates drivers/char/tty_ioctl.c
Greg Kroah-Hartman <gregkh@suse.de>
Alan Cox <alan@redhat.com>
Alan Cox <alan@linux.intel.com>
Alan Cox <alan@lxorguk.ukuu.org.uk>
Mike Frysinger <vapier@gentoo.org>
Alexey Dobriyan <adobriyan@gmail.com>
linux-kernel@vger.kernel.org

Using --remove-duplicates could eliminate multiple maintainers that
share the same name but not the same email address.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>