[$] CPython, C standards, and IEEE 754

Perhaps February was "compiler modernization" month. The Linux kernelrecently decided to move to the C11 standardfor its code; Python has just undergone a similar process fordetermining which flavor of C to use for building itsCPython reference implementation. A calculation in the CPython interpreterwent awry when built with a pre-release version of the upcoming GCC 12; thatregression led down a path that ended up with the adoption of C11 for CPython as well.