Updated clang and gcc targets. Fixed spelling of LIMITS, which breaks the
  gcc_auto_sizeof.yml build.
 Commented -Wunreachable-code, Unity won't build on OSX clang with it,
  error in unity.c:769 & 932: 'default: break;' case.

rearranged project to centralize all self-test stuff under test directory. only pull in includes when required.