HHVM: default config is disabled by -n [Closes #159]; minimal version is 3.3.0
HHVM: hide stack trace for uncatched exceptions [Closes #160]

Without this option, Fatal Error stack trace is printed even the set_exception_handler() is used (e.g. AssertException printing).
tests: workaround for missing Closure::bindTo() in HHVM
tests: Runner.multiple-fails.phpt partial HHVM fix
tests: Runner.multiple-fails.phpt fix [Ref #162]
Merge pull request #165 from milo/pull-hhvm-fixes

HHVM fixes - tests pass hunting