Fix segmentation fault when invoking __callStatic()
Enable valgrind on Travis
Install valgrind on travis
Work around PHP bug causing crash
Disable valgrind again

run-tests.php -m sucks -- REPORT_EXIT_STATUS is broken and
--show-mem is not available. Which makes this really useless as I
can't see the valgrind output.
Add idea to solve this method call handler in PHP < 5.6