Add missing WASAPI macros for resampling

[Crunkle]

The macros needed to fix #194 are not defined by the MinGW headers (see here).

[cgutman]

Have you tried getting them added to MinGW upstream? I think that's the best approach here, since they are officially documented flags.

[Crunkle]

For sure, I will submit a merge when possible, so feel free to reject this if we're out of scope.

The rationale behind adding this here is based on the fact that the majority of systems will continue using outdated headers for the time being (either from package managers or MXE). It seemed a shame to cut off all older versions and complicate the build process simply due to two macros.

[cgutman]

In that case, I think it's fine to do both, but we should definitely get MinGW fixed so we don't have to carry these defines forever.