Add prefix arg handling to indent-for-tab-command

Add prefix arg handling to indent-for-tab-command

(indent-for-tab-command): Rigidly indent the following sexp along
with the current line when a prefix arg is given in the
non-active-region case.  Specify raw prefix in interactive spec.
Simplify main indentation logic to get rid of the conditional call
to `indent-according-to-mode' (it just ended up calling
`indent-line-function' in all cases anyway, which can be done more
simply here).  Remove unnecessary test of ARG in active region case.

Revision: emacs@sv.gnu.org/emacs--devo--0--patch-964