Simple tests to check ATD -> OCaml <-CConv-> JSON.

An explicit set of tests that individually (and incrementally) consider
the different possible ATD's, then makes sure that the code generated
for each ATD can be passed valid OCaml that can then be converted to and
from JSON.
Merge PR #8 (@rleonid, tests)

Conflicts solved:
	src/lib/atd2cconv.ml
gen: Update generated META file