The vast majority of this is fixing up `char *` that should be `const char *`
but a handful of other fixes, like potential buffer overflows that GCC
noticed, etc, were applied as well.
This removes `-Wno-write-strings` from CMakeLists.txt, as it is no longer
necessary, as there is no longer a flood of compiler warning spam when
building.
This does not fix all compiler warnings; there are still a handful, and they
are legitimate, but they can be dealt with in a future commit.
Implementing byteswap functions by using "backported" from C++23 std::byteswap.
Adding unittests based on GoogleTests. To enable it add `-DBUILD_TESTING=ON` to cmake.
