3.2

1. #13 which resolves #11
2. Update T* to use std::add_pointer_t which ensures reference types are handled better.
3. Make calling convention defines available project-wide.
4. Add new specializations to enable more native syntax
   function_ptr<void __stdcall()> is now valid for stdcall, as are all the other conventions and variadic functions.
5. Add new helper, is_calling_convention_active to determine if a calling convention is active for a specific architecture.
6. Clean up various smaller warnings.