The non-C/C++ standard defined math constants require
`-Xcc -D_USE_MATH_DEFINES` when using the `ucrt` module. Instead,
provide them through the wrapper `MSVCRT` module as aliases so that the
user does not need to be aware of this in practice.
Repairs the Windows build of `_Differentiation`.
Although technically these shouldn't be needed on Windows since there is
no compatibility to maintain since there is no version that exists
previously. However, this will ease porting of sources to the platform.
It also ensures that future tests added cover windows as well.
This adds the swiftMSVCRT module which is similar in spirit to swiftGlibc and
swiftDarwin, exposing the Microsoft C Runtime library to swift. Furthermore,
disable pieces of the standard library which are not immediately trivially
portable to Windows. A lot of this functionality can still be implemented and
exposed to the user, however, this is the quickest means to a PoC for native
windows support.
As a temporary solution, add a -DCYGWIN flag to indicate that we are building
for the cygwin windows target. This allows us to continue supporting the cygwin
environment whilst making the windows port work natively against the windows
environment (msvc). Eventually, that will hopefully be replaced with an
environment check in swift.
