Clang is now called AppleClang on Mac OS.
[IO] Specify full path in include.
[ML] Specify full path in includes.

Also removed unnecessary includes.
[ML/Tests] Fix warnings in tests.
[GL] Specify full path in includes.
[ML] Make all include paths explicit.
[ML] Include declaration headers first.
Merge pull request #498 from endJunction/FullPathInIncludes

Full path in includes
Merge pull request #499 from endJunction/FixWarningsInMeshLibTests

Fix warnings in MeshLib tests.