Fix in testsuite: `make one` and `make parallel`
Fix in testsuite: `make one` and `make parallel`

The `parallel` and `one DIR=...` targets currently do not work as
inteded for tests using the new 'ocamltest' framework: `one ...` has
no effect, and `parallel` only runs on old-style tests and ignores new
tests. This commit fixes this discrepancy in behavior.

gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml