Bionic/libm: Add precision-correct de-serialize sin/cos.

Modify sin/cos to improve performance while retaining bit-for-bit
accuracy with existing algorithm.

Change-Id: Iaba2dd731cd015732744705dad8bddb713b43067
libm: optimistic pow calling.

Call optimized pow optimistically and revert to full range
implementation if we detect an out-of-range input.

Change-Id: I6f3aa734adbf99484b7ff70736ef83a41e5815b8
libm: sqrt and sqrtf via ARM vsqrt instruction

Optimized sqrt and sqrtf for arm by using hardware
opcode for sqrt rather than generic slow portable
code.

Change-Id: I84694159577aef6418710548085d8149c45e0e3f