Prevent concurrent calls to EnumDevices
Prevent concurrent calls to EnumDevices

Some device filters (like the XCAPTURE-1's filter) crash when they are
enumerated concurrently from multiple threads when releasing
the IID_IBaseFilter after the first concurrent thread finishes
enumeration.

jp9000/libdshowcapture,ChristianFrisson/libdshowcapture,jp9000/libdshowcapture,upsoft/libdshowcapture