Implement ManagementQuery QueryLanguage
Implement ManagementQuery QueryString
Implement ObjectQuery
Merge pull request #784 from alesliehughes/master

Support for ManagementQuery and ObjectQuery classes
Disable ClientWebSocketTest.cs (for mobile) until the type itself is added to the mobile profile (i.e. added to mobile_System.dll.sources). Fix building/running System.dll unit tests
Add InterlockedExchange64 () based on GCC intrinsics for MinGW.

As with InterlockedCompareExchange64, MinGW appears to lack this
one from its Windows headers.