Eliminated valgrind timeouts in nightly testing.

A few tests have been consistently timing out in our nightly testing. This change fixes that mostly by

* creating .valgrind.chpl copies of the original tests
* adding .skipif on the original (do not valgrind) and the copy (only do valgrind)
* for the copy, either increasing the timeout or reducing the problem size

One of the tests seemed unimportant to run under valgrind, so I skipif'ed it without creating a copy.

Once our test system allows us to specify separate timeouts or problem sizes for valgrind (or any other configuration, e.g. baseline), the .valgrind.chpl copies can be eliminated in favor of such specifications.