* Making crc constexpr for c++14. Allows compile time CRC computation.
* Fix syntax when using c++03 or `ETL_FORCE_NO_ADVANCED_CPP`
* Remove use of `ETL_FORCE_NO_ADVANCED_CPP` option since it is no longer used.
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Co-authored-by: Zach O'Brien <zach.obrien@tortugaagtech.com>
Co-authored-by: John Wellbelove <jwellbelove@users.noreply.github.com>