Adjust test range and fix singleaccuracy tests

Adjust test range and fix singleaccuracy tests

This changes the limit of exp() tests by one ulp
to account for rounding that leads to tests failing
for a single value when the CPU uses different
denormals-to-zero modes for SIMD and non-SIMD (ARMv7).

It also fixes the singleaccuracy tests to
check the correct functions for log2/exp2/pow2/cbrt
instead of the double-precision flavors, and the
implementation of powSingleAccuracy has been
copied from the (faster) single precision type
instead of just calling the double precision version.

Change-Id: I67d027cb916c4f78f36719f9ff554e9957879763