Add support for optgroup-tags for select-fields

We currently throw an exception with setting the multiple-attribute is
attempted. If we want to implement this functionality, it might be more
sensible to make an extra commit for that.

Test against the current hhvm version

Multiple selected option would not be valid HTML.

Translation update (sr)

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

In more complex selects we may want to group options by some criteria.
HTML has the <optgroup>-tag for that purpose.

However in Order to not duplicate code, I've to move the handling of
options to the OptGroup-Class completely.

Known Issues:
-------------
* We may have more than one option with the same value and therefore
more than one option may be marked as selected.

fixes #1776

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.

Translation update (zh)

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)
  translation update
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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
  translation update
  translation update
  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.

Translation update (sr)

Translation update (sr)

inSQL password checking for authpdo

fix calculation of LastRevisionAt