Signed-off-by: Bernhard Kölbl <besentv@gmail.com>

It's used by the function to find document content type. Fixes regression
introduced by e164b8ce.

Instead of including the IDLs directly, define a local IDL that #includes them,
with XAUDIO2_VER defined, and include that generated header.

Get rid of compat.c, and use XAUDIO2_VER to modify the code in the other source
files.

Build the tests for both xaudio2_7 and xaudio2_8 using PARENTSRC, and use
XAUDIO2_VER to select between them. This mirrors the approach taken for
d3dcompiler, and makes it easier to test more xaudio2 versions in the future.

Instead of going through the class factory.

When applying a new cursor clipping rect, or to the previous foreground
thread when foreground changes, to notify it of the cursor clipping rect
being reset.

And make the allocation limits more explicit.

release_vbscode doesn't do anything if ref is 0.