[PATCH] Fix cos computation for multiple precision fallback (bz #20357)

[Siddhesh Poyarekar]

On Tue, Jul 12, 2016 at 02:22:03PM +0530, Siddhesh Poyarekar wrote:
> During the sincos consolidation I made two mistakes, one was a logical
> error due to which cos(0x1.8475e5afd4481p+0) returned
> sin(0x1.8475e5afd4481p+0) instead.
> 
> The second issue was an error in negating inputs for the correct
> quadrants for sine.  I could not find a suitable test case for this
> despite running a program to search for such an input for a couple of
> hours.

FYI, I have added this as a blocker for 2.24.

Siddhesh