In order to reduce our reliance on __builtin_{ffs, clz, ctz, popcount},
this commit removes all calls to these functions and replaces them with
the equivalent functions in AK/BuiltinWrappers.h.
This is a naive implementation based on the symmetry with `asin`.
Before, I'm not really sure what we were doing, but it was returning
wildly incorrect results.
On x86, the `fprem` and `fmprem1` instructions may produce a 'partial
remainder', for which we should check by reading a FPU flag. If we don't
check for it, we may end up using values that are outside the expected
range of values.
This is to implement constexpr template based implementations for
mathematical functions
This also changes math.cpp to use these implementations.
Also adds a fastpath for floating point trucation for values smaller
than the signed 64 bit limit.
