[ticket/12544] Update Plupload to 2.1.2.

PHPBB3-12544
Merge pull request #2457 from prototech/ticket/12544

[ticket/12544] Update Plupload to 2.1.2.

* prototech/ticket/12544:
  [ticket/12544] Update Plupload to 2.1.2.
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12544] Update Plupload to 2.1.2.