inconsistent inclusion of portaudio.h in the various platform-specific headers

[rossb]

Some platform specific headers include portaudio.h, others don't, but require the user to include it.

I think probably we should standardise the include guards for all portaudio headers on INCLUDED_PORTAUDIO_filename_H and then do something like this in the platform specific headers:

#ifndef INCLUDED_PORTAUDIO_PORTAUDIO_H #include "portaudio.h" #endif /* INCLUDED_PORTAUDIO_PORTAUDIO_H */

That avoids possible multiple inclusions without requiring inclusion of portaudio.h by the caller. The alternative is to not include portaudio.h in any of the platform specific headers...