Tool renames and 'ls-files -t' output

[Junio C Hamano <junkio@cox.net>]

The "master" branch post 0.99.6 already has the renamed tools
with backward compatibility symlinks.  I'll be sending a
patch to address an issue raised by some people separately to
see what the list thinks, and also will attempt to send out a
patch for the Pasky and Catalin heads later this week.  Also
I'll remove the ancient backward compatible environment variable
names from gitenv.c.

There were discussion on the tag 'git-ls-files -t' output uses.
I got a feeling that we might want to change them to match what
other tools give.  Here is the proposed changes:
	
    Meaning	Current		Updated

    cached	H		.
    unmerged	M		U
    removed	R		D
    other	?		?
    killed	K		K
    modified	info unav.	M

I may also be tempted to rename 'tag_removed' variable there to
'tag_deleted' for consistency.

Comments?