Trigonometric optimizations for POWER cpus

These optimizations remove most of the FP->INT conversions making
the computation done with FP operations instead. This eliminates
Load-Hit-Store (LHS) stalls on POWER, increasing performance of
hypot/hypotf (about 50% on POWER7, 25% on POWER6, and 30% on POWER5)
and sinf/cosf (30% on POWER7, 15% on POWER6, and 10% on POWER5).
(cherry picked from commit 5939fc08)