[ticket/12397] Fix sql_unique_index_exists doc block

db_tools::sql_unique_index_exists() searches for unique indexes but not
primary key indexes.

PHPBB3-12397
Merge pull request #2310 from n-aleha/ticket/12397

[ticket/12397] Fix sql_unique_index_exists doc block

* n-aleha/ticket/12397:
  [ticket/12397] Fix sql_unique_index_exists doc block
[ticket/12417] Revert "No longer allow Travis CI HHVM environment to fail."

hhvm-nightly 2014.04.16~precise introduced "Attempted to serialize
unserializable builtin class DOMElement" errors when running functional tests.

This reverts commit ff7cc77f9db66b7fddacd77f215d85cf0243b2fa.

PHPBB3-12417
Merge pull request #2324 from bantu/ticket/12417

[ticket/12417] Revert "No longer allow Travis CI HHVM environment to fai...

* bantu/ticket/12417:
  [ticket/12417] Revert "No longer allow Travis CI HHVM environment to fail."