scripts/get_maintainer.pl: add .get_maintainer.conf default options file

Allow the use of a .get_maintainer.conf file to control the default
options applied when scripts/get_maintainer.pl is run.

.get_maintainer.conf can contain any valid command-line argument.

File contents are prepended to any additional command line arguments.

Multiple lines may be used, blank lines ignored, # is a comment.

Updated scripts/get_maintainer.pl version to 0.24

Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Florian Mickler <florian@mickler.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>