Emacs: show bookmarks buffer on startup

Signed-off-by: Ratheesh S <ratheeshreddy@gmail.com>
Emacs: Enable git-commit-mode for more stgit bufs

Enable git-commit-mode for .stgit-quash.txt and .stgitmsg.txt

Signed-off-by: Ratheesh S <ratheeshreddy@gmail.com>