[ticket/11578] Add missing underscore after 'validate' function prefix

The underscore after the 'validate' function prefix for the older
functions was dropped by accident in PR #1407. This patch will add it
back.

PHPBB3-11578
Merge remote-tracking branch 'marc1706/ticket/11578' into develop-olympus

* marc1706/ticket/11578:
  [ticket/11578] Add missing underscore after 'validate' function prefix
[ticket/11580] Enable --no-interaction option on composer for travis

There is no interaction available on travis ;)

PHPBB3-11580
[ticket/11580] Enable prefer-source option (should error way less)

PHPBB3-11580
Merge remote-tracking branch 'nickvergessen/ticket/11580' into develop-olympus

* nickvergessen/ticket/11580:
  [ticket/11580] Enable prefer-source option (should error way less)
  [ticket/11580] Enable --no-interaction option on composer for travis