Portaudio should expose host API specific stream information

[PortAudio-admin]

Issue created by @robiwano

Today the PaStreamInfo struct contains no host API info of the stream. Portmixer relies on a patch that adds (unneccesarily) export symbols. PaStreamInfo should be extended to a) expose the host API type of the stream b) a void* ptr to a host API specific struct (which is defined in the host API headers) so that Portmixer can extract the information it needs.

We decided to add the hostApiType field a long time ago:
http://music.columbia.edu/pipermail/portaudio/2008-February/008314.html

[PortAudio-admin]

Comment by @robiwano

Tickets #18,#19 and #21 are related to this.

[PortAudio-admin]

Comment by @RossBencina

In case anyone queries whether we should be breaking binary compatibility by potting the host api id at the start of the struct. We already decided we're going to break things

http://music.columbia.edu/pipermail/portaudio/2008-February/008328.html
Richard Ash wrote:

yes and yes from this end - break the compatibility, add the field
where you think it fits in (at the start), increment the library version
number, and whilst you are busy breaking binary compatibility, remove
run-time struct versions as well. Some #defines would be a good idea,
but I think API versions (on the same major / minor / point scheme as
the library number) are the way to go.

[PortAudio-admin]

Comment by @RossBencina

Note that we should remove the structVersion field at the same time as adding hostApiType field, per #172

[PortAudio-admin]

Comment by @RossBencina

TRAC migration: propagating ticket status from TRAC