Bionic/libm: fast neon pow() for small x,y

Signed-off-by:  Paul Beeler <sparksco@gmail.com>

Add a fast neon version of pow() suitable for relatively small
positive x and y (between 0 and 4).  Run the standard
implementation in all other cases.  Gives approximately 60%
performance improvement to AnTuTu FPU score.

Change-Id: I9234d37eaa6a815d1e619375f5b049c4ec88f557

Fixup e_pow

Conflicts:
	libm/Android.mk
	libm/arm/e_pow.S
Fixup string handling routines for QCOM devices.

Conflicts:
	libc/Android.mk

Change-Id: I74cadd6cd9812b073d7377d04430c1ee13ae9761