Also allows scientific format to be forced for all floating point output.
NAN and INF outputs now follow case settings, as does the new scientific exponent letter. 'e' or 'E'.
Updated CI scripts
#786 u8string
#783 Cannot insert existing value to full set
#781 etl::multi_span::iterator::operator *() fails if first span is empty
#780 endian enum_type produces useless-cast warnings
#779 hash.h: warnings produced with -Wfloat-equal
