[ticket/12975] Fix the construction of phpbb\auth\provider\db for Oauth

PHPBB3-12975
[ticket/12900] Fix potential avatar size box overflow

PHPBB3-12900
[ticket/12856] Copy plupload images to prosilver dir

PHPBB3-12856
[ticket/12856] Remove images from assets/plupload/img/

PHPBB3-12856
Merge remote-tracking branch 'PayBas/ticket/12856' into develop-ascraeus

* PayBas/ticket/12856:
  [ticket/12856] Remove images from assets/plupload/img/
  [ticket/12856] Copy plupload images to prosilver dir
Merge pull request #2876 from PayBas/ticket/12900

[ticket/12900] Fix potential avatar size box overflow
Merge pull request #2872 from Nicofuma/ticket/12975

[ticket/12975] Fix the construction of phpbb\auth\provider\db for Oauth

* Nicofuma/ticket/12975:
  [ticket/12975] Fix the construction of phpbb\auth\provider\db for Oauth
[ticket/12986] Fix detection of common words in search

$search->get_common_words() call goes before the split_keywords() call,
but $search->common_words array is being generated
within the function $search->split_keywords(). Thus, get_common_words()
returned an empty array instead of common words array.

PHPBB3-12986
Merge pull request #2881 from rxu/ticket/12986

[ticket/12986] Fix detection of common words in search

* rxu/ticket/12986:
  [ticket/12986] Fix detection of common words in search
[ticket/12984] Remove blank line when no forum description shown

Add a conditional for forum description and move the <br /> within it.
Currently if there is no forum description but there is
1. a displayed forum moderator and/or
2. a displayed sub-forum
a blank line is added in place of the description

PHPBB3-12984
Merge pull request #2886 from Oyabun1/ticket/12984

[ticket/12984] Remove blank line when no forum description shown

* Oyabun1/ticket/12984:
  [ticket/12984] Remove blank line when no forum description shown
[ticket/12996] Fix reliability issue in flock test.

$delta was always an int - so, this test would sometimes fail if you
happened to call time() /very/ close to a 1s boundary.

Found by HHVM's continuous testing.

PHPBB3-12996
Merge pull request #2892 from bantu/ticket/12996

[ticket/12996] Fix reliability issue in flock test.

* bantu/ticket/12996:
  [ticket/12996] Fix reliability issue in flock test.