added missing INSTALL_ROOT
added missing INSTALL_ROOT
Merge branch 'PHP-5.5' into PHP-5.6

* PHP-5.5:
  added missing INSTALL_ROOT
Merge branch 'PHP-5.6'

* PHP-5.6:
  added missing INSTALL_ROOT
Merge branch 'pull-request/859'

* pull-request/859:
  added missing INSTALL_ROOT