Fix sin, cos, tan in non-default rounding modes (bug 3976)

[David Miller]

From: Richard Henderson <rth@twiddle.net>
Date: Sat, 03 Mar 2012 10:05:33 -0800

> Yeah, well, turning it into an always_inline static function
> should be trivial, right?

It's CPP ifdef overridden in header files, so not so trivial.