Incorporate MSVC's `__declspec(noalias)`#54

Microsoft's `__declspec(noalias)` is [documented ](https://docs.microsoft.com/en-us/cpp/cpp/noalias?view=msvc-170) as: > noalias means that a function call doesn't modify or reference visible global state and only modifies the memory pointed to directly by pointer parameters (first-level indirections). So it is analogous to gcc/clang `__attribute__((const))`. Currently `HEDLEY_CONST` does not generate it.