* use static_assert directly. Raze is C++17, no need for that macro shit.
* removed CONSTEXPR - I seriously fail to see the use here, many of the functions marked as CONSTEXPR cannot possibly even be constant evaluated so the declaration makes no sense. Removed most of these and replaced the valid ones with the official constexpr keyword.
* got rid of EDUKE_PREDICT_FALSE - this makes zero sense in script parsing code, at best it will save a few microseconds. Clean code wins.
* replaced Blrintf with xs_CRoundToInt. Shitty name is shitty name, even if derived from POSIX.
* replaced Bstr*casecmp with str*icmp. As these get defined in the CMake project based on actual compiler checks they are preferable here.
* removed lots of other stuff that is not needed with a minimum compiler requirement of C++17.
