sincos()

[staticfloat]

Adds in implementations for sincos(), an efficient method of computing the sine and cosine of the same angle.

I'm not entirely sure how to test the 80-bit long double versions, so I haven't attempt to make it more efficient than simply calling sin/cos in succession.

[ViralBShah]

Passes tests for me.

[ViralBShah]

Out of curiosity - why did you not just implement the 4-line trivial version that was in libm-test.c?

[staticfloat]

Perhaps I'm a glutton for punishment, but I wanted to see if the work that is being saved by performing the common calculations only once was significant. Turns out it's not, (at least, not with -O3 enabled. It seems compilers are smart enough to remove the redundant work after all!) but it was an interesting jaunt through sin/cos implementation at the least.

[ViralBShah]

:-)

[nolta]

Whoa, this isn't a formatting change.

So is this faster than the old code?

[staticfloat]

This change is paired with the additions below on lines 58-59; I swapped the inequalities to instead match the order found in s_sinf.c for easy comparison between the two. There should be no difference in performance, unfortunately. ;)