Added regression test for #1340.

Child process must produce > 4096 bytes on STDERR (e.g., a large PHP backtrace).
Fixed #1340: Reading from STDOUT or STDERR hangs forever on Windows if the output is too large.

See https://bugs.php.net/bug.php?id=51800
Ignore irrelevant test result differences.
Ignore irrelevant test result differences on HHVM.
Merge pull request #1345 from sun/runner-isolation-stderr-fatal-41

Process isolation blocks infinitely upon fatal error in child process