Update phpenv with a fix to config-rm.

Fixes travis-ci/travis-ci#999.
Support PHP 5.3.23, 5.4.13 and 5.5.0beta1.

Notes for PHP 5.5:
* ZTS support has been disabled on 5.5 because of
  https://bugs.php.net/bug.php?id=64373.
* xdebug is now available on this version!
Merge branch 'master' into bluebox