Test against the current hhvm version

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Turn off the hhvm JIT to speed up the hhvm unit tests.

Source for why the JIT is bad for unit testing: facebook/hhvm#6979

This provides the current HHVM version (3.15.3 as of this PR) and will track with each release (i.e. will be 3.16 when 3.16 is released.

If testing against HHVM LST versions is desired follow this guide. https://docs.travis-ci.com/user/languages/php#HHVM-versions

Should be able to change to container based Trusty after Q1-17 https://blog.travis-ci.com/2016-11-08-trusty-container-public-beta/

Now each command is checked within it's own test on a completely clean
install. Hopefuly this also takes care of the flaky test behavior seen
at Travis occasionally.

Some of our tests require that at least one second has passed before
they can continue because our revisions depend on the Unix Timestamp.

Currently we use a sleep(1) for this. However this always waits a whole
second, even if the next second is already much closer or maybe already
here - especially when some processing has been done since the last
operation.

This new method waits for the next second by checking the time every
10th of a second. This might speed up some of our tests a bit.

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Use composer installed phpseclib

this is not supported, yet: https://github.com/facebook/hhvm/issues/2745

Added file-in-use reference to media-manager

* master: (54 commits)
  updated geshi
  authpdo - use type safe comparison on passwords. fixes #1765
  removed unneeded files from random_compat
  Use cryptographically secure pseudo random number generator (CSPRNG)
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  or maybe I only now figured out the right travis config :-/
  disable 7.1 testing completely
  allow 7.1 failures until it's released #1682
  DE translation for key 'protected'
  Use 'Benachrichtigung' instead of 'Notifikation'
  Fix spelling of some terms (lower to upper case)
  DE translation for key: addUser_error_missing_pass
  DE translation for keys: update_name, update_mail
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  Implemented interwiki substitution for external images (issue #1614).
  ...

Uses paragonie/random_compat instead of insecure home-brewed code.

It's NEVER fine to fall back to mt_rand() for secure random.

Fixes #1760.

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inSQL password checking for authpdo

fix calculation of LastRevisionAt

added debug prints to better figure out when LDAP has search issues.

Return valid xml when XML-RPC interface not enabled

Implemented interwiki substitution for external images (issue #1614).

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currently phpseclib throws an error (about a deprecated function).
errors do not count as failures, so we can't skip them. so for now
7.1 testing is removed again.