Prepare release
Whitelist external entities for HHVM/libxml.

Refs: facebook/hhvm@842d6fb
Simplify whitelisting external entities for HHVM/libxml.
Merge branch '4.1' into 4.2
Merge branch '4.2' into 4.3
Merge branch '4.3'
Merge branch 'master' of git://github.com/sebastianbergmann/phpunit