Bug fixes and better portability

This release adds several small features while fixing bugs and improving portability.
New features : ++ and -- operators, fpclassify, and formatting in ostream << operator.
Fixed bugs : ldexp and frexp.
Improved portability : compiler feature detection is now improved and the library is now tested on macOS and 32-bit arm. Although not added to the CI configuration, it is confirmed that the library passes the self test on risc-v systems.