C TAP Harness 4.2

The functional change in this release of my test framework for C programs is the addition of a new is_blob test function. This is equivalent to ok(memcmp(...)) but it reports where the two memory regions differ as a diagnostic. This was contributed by Daniel Collins.

Otherwise, the changes are warning fixes and machinery to more easily test with warnings. C TAP Harness now supports being built with warnings with either GCC or Clang.