MMDevAPI: IAudioSessionEnumerator returns nonsense session count and leaks memory

Changes introduced in Add implementation for IAudioSessionEnumerator are preventing Special K from working.

The previous stub implementation was fine, but with the introduction of the session enumerator, Special K cannot be used in any game without leaking memory and quickly crashing (unless I activate a Wine-specific workaround added in Special K 24.10.19).

Here is the implementation of Special K's session enumeration if it helps. This works just fine on Windows with no leaks or the crazy number of sessions returned by IAudioSessionEnumerator::GetCount (...).

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While reviewing the changes above, I noticed a problem with the Critical Section guarding the session list.

Critical Section guarding audio sessions is entered twice, never exited.
2762b7a

I think the second sessions_lock () should be sessions_unlock ()

Start with the implementation introduced by commit 2762b7a and trace IAudioSessionEnumerator::GetCount and the session-list locking, using Special K's linked session-enumeration code as a behavioral reference. Done means the count is sensible, enumeration no longer leaks or causes crashes, and the critical section is balanced; no test file is named in the issue.