Eliminated valgrind timeouts in nightly testing.

A few tests have been consistently timing out in our nightly testing.
This change fixes these timeouts by:

* create .valgrind.chpl copies of the original tests

* add .skipif on the original (do not valgrind)
  and on the copy (only do valgrind)

* for the copy, either reduce the problem size or
  (where that is not possible or practical) increase the timeout or 

* overflowInComputeBlock.chpl seemed unimportant to run under valgrind,
  so skipif 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.

One issue I debated is whether to create the .valgrind.chpl copy
of the test using symlinks (see e.g. #755), 'use', or just plain copy.
I haven't been consistent here, in most cases created plain copies
for non-.chpl files and 'use' + call the other main() for .chpl.
These tests:
  capture.chpl, captureAppearsToWork, stress.chpl
cannot use 'use' because of a known bug - cannot 'use' a module
whose init has 'begin's outside of any 'sync'.


TEST DETAILS
  [xx/yy] - time it takes on an idle machine with valgrind / without valgrind

io/ferguson/ctests/qio_test.test.c
  [<26 min/<1 min]
  increased the timeout to 2000

parallel/begin/sungeun/capture.chpl
parallel/begin/sungeun/captureAppearsToWork.chpl
  [5s/?]
  the test starts 250 'begin's at the same time,
    each waiting on a 'single' var
    5s is time under valgrind on an idle machine;
    since we oversubscribe the machine for nightly testing,
    I suppose that it causes the execution time to increase a lot
  reduced the problem size to 10

release/examples/benchmarks/lulesh/lulesh.chpl
  [<12min/7s] for execopt #4
  increased the timeout to 1000

studies/hpcc/PTRANS/PTRANS.chpl
  [>35 min/10s]
  reduced the problem size

studies/lammps/shemmy/p-lammps-n1.chpl
  [>21 min/32s]
  increased the timeout to 2000

studies/lammps/shemmy/p-lammps-n2.chpl
studies/lammps/shemmy/p-lammps-n4.chpl
  these are identical to -n1;
  should no longer be tested under valgrind due to #755

types/range/bradc/overflowInComputeBlock.chpl
  [<35 min/16s]
  skipif for now
  this test does not test its original intention IMO
  I have an email to Brad about it
  we could alternatively reduce the problem size for valgrind

types/single/sungeun/stress.chpl
  [1s/?]
  similar to capture.chpl above
  reduced the problem size to 10