[ticket/12275] Fix a bug on the event "core.modify_username_string"

Call the event "core.modify_username_string"
also if $mode is "colour", "username" or "profile".

PHPBB3-12275
[ticket/12384] Run Travis CI HHVM tests against MySQLi instead of MySQL.

HHVM MySQLi has been fixed and works for us now.

PHPBB3-12384
[ticket/12407] Allow changing of post_data, etc. at end of posting.php

The current event core.posting_modify_template_vars is just ran using dispatch
but it doesn't pass any data from posting.php to the listener. Because of that,
it's not possible to know anything from posting.php and therefore limits the
use cases of this event. This will change it to allow similar actions as with
the event core.modify_posting_parameters.

PHPBB3-12407
[ticket/12407] Add message_parser as passed variable to event

PHPBB3-12407
[ticket/12275] Change if (empty) to if (!isset)

PHPBB3-12275
Merge branch 'develop-ascraeus' of https://github.com/phpbb/phpbb into ticket/12407

Conflicts:
	phpBB/posting.php
[ticket/12407] Assign template variables again after merging develop-ascraeus

PHPBB3-12407
[ticket/12407] Merge @change in doc block of event

PHPBB3-12407
[ticket/12025] Post Preview no longer shows warnings

https://tracker.phpbb.com/browse/PHPBB3-12025

PHPBB3-12025
[ticket/12025] Don't show any error on preview if the message is empty

PHPBB3-12025
[ticket/12025] Fixing the condition....

PHPBB3-12025
[ticket/12431] Add has_poll icon to topiclists

PHPBB3-12431
[ticket/12451] Split TOO_FEW_CHARS_LIMIT for plurals

PHPBB3-12451
[ticket/12451] Split TOO_MANY_CHARS vars for plurals

PHPBB3-12451
[ticket/12451] Use new line to concatenate strings

PHPBB3-12451
[ticket/12451] Remove duplicated lang var

PHPBB3-12451
[ticket/12270] Corrent post and topic approval notification message

When you submit a post with needed approval (say user A), and then
it gets approved by another user (user B), a subscribed user (user C)
to that forum would receive a notification indicating:
-A has replied to topic 'New Topic' in the forum 'xyz'.
The expected result would be:
-A has posted a new topic 'New topic' in the forum 'xyz'.
This has fixed by adding a TOPIC_ID template variable to
mcp_post.html and, in there, depending if the first post is the topic's
first post or not, add a input's with name topic_id_list[] or
post_id_list[] and then the respective value (TOPIC_ID or POST_ID).

PHPBB3-12270
[ticket/12270] Correct post&topic approval msg, no template changes

Following the previous commits, this patch removes the changes
done to templates to depend only on code, as suggested by
@nickvergessen.
All previous modifications have been removed, with another one
which checks, in the approve_posts() function, if it is sending a
notification for post approval and it is the first one in the
topic, send notification indicating that the topic has been
approved (and not the post). If not the first post in the topic,
do just as before (send a notification about a newly approved
post).

PHPBB3-12270
[ticket/12270] Reverted templates

Some lines in the templates  were not reverted correctly,
so it's done now.

PHPBB3-12270
[ticket/12270] Correct notifications for posts/topics now working

This patch should finally work correctly: Add the correct
notification for post/topic approval without touching templates.

This has been done by calling the function approve_topics()
inside the approve_posts() function. It's the simplest way for
this to work correctly. There may be a call to the DB but other
ways (if any), without touching templates,  would have been too
messy for a function like this.

PHPBB3-12270