Optimization for tiny x in cos and sin

Optimization for tiny x in cos and sin

Subset of FreeBSD commit 4339c67c485f0b1f7699863fc29f6c06862d1dde:
Moved the optimization for tiny x from __kernel_{cos,sin}[f](x) to
{cos_sin}[f](x) so that x doesn't need to be reclassified in the
"kernel" functions to determine if it is tiny (it still needs to be
reclassified in the cosine case for other reasons that will go away).
...

Parts of the original change were applied separately before.

Suggested by kettenis@

OK mbuhl@, tested by mbuhl@ and phessler@