Prevent audio thread from starving UI thread from CSoundGen::m_csAPULock #90

Job	Run time
build-matrix (x64, Release)	4m 11s
build-matrix (x64, Debug)	4m 0s
build-matrix (x64, ASAN-Release)	3m 51s
build-matrix (x64, ASAN-Debug)	3m 35s
build-matrix (Win32, Release)	4m 36s
build-matrix (Win32, Debug)	4m 27s
build-matrix (Win32, ASAN-Release)	3m 53s
build-matrix (Win32, ASAN-Debug)	3m 45s
	32m 18s

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