Floating-point review

I'm looking for someone who known more about floating-point than I do
to review one of me changes. The change in question adds 6 new
functions to the ARM libc to perform floating-point comparisons. These
functions are required as part of the ABI spec.

The review is at [1]. I am mostly interested in having someone check
__aeabi_cfcmpeq_helper and __aeabi_cdcmpeq_helper are correct. They
should both return when either argument is a quiet NaN unless one is a
signalling NaN for floats and doubles respectively.

These functions are used by a functions that is defined to not raise a
floating point exception with comparing with quiet NaNs and all
comparisons with signalling NaNs could potentially raise an exception.
Because of this requirement these functions are used to filter out the
cases we have one or more quiet NaNs and no signalling NaNs.

Andrew

[1] https://reviews.freebsd.org/D872