According to documentation, if the argument of std::exp is zero, one is returned.
However we want the return value to be also zero in this case so no audio is played.
These two macros being used in tandem were used prior to the
introduction of UNIMPLEMENTED and UNIMPLEMENTED_MSG. This provides
equivalent behavior, just with less typing/reading involved.
This was created with the unfinished resampling PR in mind.
As the resampling is now on the audio thread, we don't need to care about this here any more.
Preserves the meaning/type-safetiness of the stream state instead of
making it an opaque u32. This makes it usable for other things outside
of the service HLE context.
