git-status: wording update to deal with deleted files.

git-status: wording update to deal with deleted files.

If you do:

	$ /bin/rm foo
	$ git status

we used to say "git add ... to add content to commit".  But
suggsting "git add" to record the deletion of a file is simply
insane.

So this rewords various things:

 - The section header is the old "Changed but not updated",
   instead of "Changed but not added";

 - Suggestion is "git add ... to update what will be committed",
   instead of "... to add content to commit";

 - If there are removed paths, the above suggestion becomes "git
   add/rm ... to update what will be committed";

 - For untracked files, the suggestion is "git add ... to
   include in what will be committed".

Signed-off-by: Junio C Hamano <junkio@cox.net>