Clang 8 CI build added.
Clang 8 CI build added.

mattgodbolt/seasocks,offa/seasocks,mattgodbolt/seasocks,mattgodbolt/seasocks,mattgodbolt/seasocks,offa/seasocks,offa/seasocks,mattgodbolt/seasocks,offa/seasocks,offa/seasocks,offa/seasocks,mattgodbolt/seasocks