Switch HHVM off of container

[photodude]

Pull Request for hhvm is out of date and segfaulting with phpunit Issue.

Summary of Changes

Use Trusty build for HHVM to get HHVM 3.13.1 which solves a segfault issue in the HHVM 3.6.x testing
use fast finish to let allow failures continue to run yet still report the completed required tests on time. (trusty builds can be slow)

Note: although this get's us testing on a supported HHVM version and solved the segfault issue, there is still a Fatal error: request has exceeded memory limit issue with a test. This test error should not hold back accepting this PR.

Testing Instructions

Merge by code review

[rdeutz]

@photodude do you have na idea what we can do to work around the memory limit? I assume setting the memory_limit to a high value is not the solution if possible.

[andrepereiradasilva]

reggarding memory limit, could this work? http://blog.simplytestable.com/setting-the-php-memory-limit-for-travis-ci/

[photodude]

@rdeutz I tested with the default Trusty memory limit for hhvm using ini_get("memory_limit") returns 17179869184 available and fails

Eventually I found a way to change the hhvm memory limit and set it to a lower limit then to unlimited. @andrepereiradasilva the post you referenced was my starting point (see my comment on that post), but that resulted in a different error cp: cannot create regular file. I did find a way around that
for unlimited ini_get("memory_limit") returns 9223372036854775807
And that still fails.

In all cases memory_get_peak_usage() returns 2097152

The Test causing Fatal error: request has exceeded memory limit in /home/travis/build/photodude/joomla-cms/libraries/vendor/phpunit/php-timer/src/Timer.php on line 97 is 'FinderIndexerStemmerPorter_EnTest::testStemWrongLanguage'"

I since I used --debug with phpunit to acquire a list of tests (an incomplete list) that errored or failed.
You can get that list in issue #10220
I have reported the slow builds with Trusty to Travis-CI travis-ci/travis-ci#5980

I'm trying to see if there is a way to skip the tests having issues so we can get a report of the other issues. So far the --exclude-group didn't work (even with adding the @group to the failed test).