Fix aliasing issues with GCC 4.8.0 and Python 2.x

Reverting the previous attempts at fixing the miscompiles
with GCC 4.8 and switch to the -fstrict-aliasing save variant
that works also on ARMv7 (where the previous workaround failed).

See http://www.python.org/dev/peps/pep-3123/ for the explanation
and the inspiration for the fix.