Update/improve sy-git-log, sy-git-blame.

Update/improve sy-git-log, sy-git-blame.

With this change, viewing the log looks much nicer with a little
font-locking.  You can also pass on custom git log options via a 2nd
prefix arg.

	* sy-git.el (sy-git-log): Allow setting custom git log options via
	a 2nd prefix arg. Add some font-locking. Don't use electric-help.
	(sy-git-log-font-lock-keywords): New.
	(sy-git-blame): Don't use electric-help, shrink the window if the
	buffer is smaller.

Signed-off-by: Steve Youngs <steve@sxemacs.org>