T3/T3 mul_2 and addmul_2

[David Miller]

From: Torbjorn Granlund <tg at gmplib.org>
Date: Mon, 25 Mar 2013 19:45:27 +0100

> I cannot recall which edits I made between these variants.  If only the
> checked-in code has fluctuations, then it should be no problem finding
> an edit which avoids them.  If both variants have fluctuations, then it
> will be harder, of course.

I'll try to figure it out.  One thing is that the T4 is really sensitive
to function and loop alignment, so the issue could be in that area.