Fix a subtle bug in the OSX workaround for rar-opencl. Found by the
max-length self-test. Also bump max length to 22 and drop a couple
of obsolete "FIXME" in unrar code.
Merge branch 'unstable-jumbo' into bleeding-jumbo

* unstable-jumbo:
  Fix a subtle bug in the OSX workaround for rar-opencl. Found by the max-length self-test. Also bump max length to 22 and drop a couple of obsolete "FIXME" in unrar code.