git-mailsplit: with maildirs not only process cur/, but also new/

git-mailsplit: with maildirs not only process cur/, but also new/

When saving patches to a maildir with e.g. mutt, the files are put into
the new/ subdirectory of the maildir, not cur/.  This makes git-am state
"Nothing to do.".  This patch lets git-mailsplit additional check new/
after reading cur/.

This was reported by Joey Hess through
 http://bugs.debian.org/447396

Signed-off-by: Gerrit Pape <redacted>
Acked-by: Jeff King <redacted>
Acked-by: Alex Riesen <redacted>
Acked-by: Fernando J. Pereda <redacted>
Signed-off-by: Junio C Hamano <redacted>