Implements #364 (closed). We:
- Detect whether the POSIX library implements the barriers or not.
- If they are implemented define the SWIFT barriers as the POSIX ones.
- If not use an alternative, simple, implementation.
- Be verbose about the implementation being used.
- Update the autotools macro that sets pthread flags to the latest version. Should handle OSX in a better way.
- Detect whether FPEs can be raised on this system and set the appropriate macro.
- Update the INSTALL.swift with instructions for OSX.
- Detect Skylake (mobile and desktop) and set the appropriate architecture flags.
- Fix the dump and logger tests to write unique files to /tmp/ and delete them once done.