* Better dependency tracking for unit test building and linking, and

* Better dependency tracking for unit test building and linking, and
  auto-generated headers (metakind.h etc.), so they don't have to be
  recompiled every time.  This drastically improves build time when
  only small updates are made.

* Added "memory.h" unit test header for checking out-of-memory
  conditions.  cdlist_black uses it.

* Added helpful output when you "make lcov" in a non-coverage-enabled
  build.

* Removed strict aliasing warning when compiling metakind.h header
  with optimization on.

* Removed const version of NodeBuilder::operator Node()---it was
  poorly performing, better to not permit it---and fixed the
  convenience builders to use the non-const version
  (re: code review #63)

* Color-coded test output on capable terminals.

* Fixed some warnings in unit tests.