[ticket/11538] Add unit tests for phpbb_validate_hex_colour().

PHPBB3-11538
[ticket/11538] Compare to '' instead of using empty(), so '0' does not pass.

PHPBB3-11538
[ticket/11538] Cut functional tests down a bit as these are more expensive.

PHPBB3-11538
Merge remote-tracking branch 'remotes/bantu/ticket/11538' into develop-olympus

* remotes/bantu/ticket/11538:
  [ticket/11538] Cut functional tests down a bit as these are more expensive.
  [ticket/11538] Compare to '' instead of using empty(), so '0' does not pass.
  [ticket/11538] Add unit tests for phpbb_validate_hex_colour().
[ticket/11575] Correct test_cross_join() to test_order_lower().

This test does not do any cross joining, it only tests ORDER BY LOWER(...).

PHPBB3-11575
[ticket/11576] MySQL unit tests: Enable STRICT_TRANS_TABLES and others.

PHPBB3-11576
Merge remote-tracking branch 'bantu/ticket/11575' into develop-olympus

* bantu/ticket/11575:
  [ticket/11575] Correct test_cross_join() to test_order_lower().
Merge remote-tracking branch 'bantu/ticket/11576' into develop-olympus

* bantu/ticket/11576:
  [ticket/11576] MySQL unit tests: Enable STRICT_TRANS_TABLES and others.
[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