Sort output of Functions/ref-return-intent.chpl test.

On a cray with a WLM (e.g. slurm) the output of this test is not in the same
order. Presumably the WLM is handling the stdout vs. stderr slightly different,
which results in the different ordering. Regardless, sorting the output with a
.prediff will ensure the test passes.
Merge pull request #595 from thomasvandoren/fix-spec-test-for-cray-testing

Sort output of Functions/ref-return-intent.chpl test.

On a cray with a WLM (e.g. slurm) the output of this test is not in the same
order. Presumably the WLM is handling the stdout vs. stderr slightly different,
which results in the different ordering. Regardless, sorting the output with a
.prediff will ensure the test passes.