[ticket/12794] Properly validate google+ field against valid character set

PHPBB3-12794
Merge pull request #2836 from marc1706/ticket/12794

[ticket/12794] Properly validate google+ field against valid character set

* marc1706/ticket/12794:
  [ticket/12794] Properly validate google+ field against valid character set
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12794] Properly validate google+ field against valid character set