A bit late, but I have now discovered that it doesn't build with PortAudio version 19. Those idiots changed the API in a backwards-incompatible way.
Re: problems compiling
I'm not sure what's causing those errors, but it looks like you unpacked portaudio inside the mhwaveedit source directory. Could you try moving the portaudio directory somewhere else, compile and install portaudio, and then compile and install mhWaveEdit?
Maybe you don't need portaudio at all? mhwe supports both OSS and ALSA directly. If you don't need portaudio, you can run configure with the --without-portaudio option.