Handling ASIO buffer size changes

[npostavs]

I've been working on adding portaudio support to Jamulus (jamulussoftware/jamulus#870).

One thing I found was that portaudio's API doesn't provide a way to handle changes in ASIO buffer size. The result is that when the user changes the buffer size in the ASIO driver control panel, the sound all of a sudden gets an annoying buzzing distortion. Jamulus' current ASIO code handles this correctly.

I will make a pull request from the patch I used to fix this problem shortly.

A user on the mailing list pointed out a similar issue affects WASAPI device sample rate; that doesn't affect my use-case since Jamulus only supports 48kHz and so there won't be any use in reacting to sample rate changes.

[philburk]

Fix #519 may be an alternative. We need to reconcile these two PRs.