Bionic/libm: Prefer branches and VFP ABI.

For internal functions set gcc attribute "aapcs-vfp" for ARM
and use -fno-if-conversion to prefer branches over predicated
instructions (improves performance on architectures with good
branch prediction).

Change-Id: I8424e0e82a19d35e7e3b6e3e122dcdecdd5426fd
Bionic/libm: add assembly versions of sin/cos.

Add assembly versions of sin/cos with integrated remainder pi/2
calculation.  Directly extracted from binary libm.so compiled with
__ieee754_rem_pio2 calls inlined.

Change-Id: Ia093f420e58e794635e3a5f09e8236ae7601f1f6
Bionic/libm: Pow optimizations and bug fixes.

Use VFP calling convention for pow_neon handoff function by default.
Fix register usage collision between two different polynomial
coefficients in pow_neon.  Remove conditional execution in pow_neon
and replace with branching.

Change-Id: I76095f4a006e2fb01a53943b66fd69bfa1fd3033