add more missing round defines for compat/msvc.h

[markwkidd]

Earlier MSVCs are missing some math.h functions that other compilers have. There is already a #define for roundf in msvc.h that works around one of the missing round functions.

I thought I was going to need one or two more round functions so I drafted two additions, but it turns out I do not have a use case at the moment to test these with. For now I'm including the existing roundf define below for reference, along the two new drafts.

#define roundf(in) (in >= 0.0f ? floorf(in + 0.5f) : ceilf(in - 0.5f))
#define roundd(in) (in >= 0.0  ? floor(in + 0.5)   : ceil(in - 0.5))
#define roundl(in) (in >= 0.0  ? floor(in + 0.5)   : ceil(in - 0.5))