Log Message:
Update to phonon 4.7.2

* Fix CMake 3 compatibility by synchronizing the FindQt4.cmake module from
  kdelibs git.
* Prevent possible internal infinite loop call chains when trying to handle
  backend construction in simulation mode (i.e. without actual backend
  being installed on the system).
* When not building with PHONON_INSTALL_QT_EXTENSIONS_INTO_SYSTEM_QT, make
  sure that the relative Qt paths are set according to whether the build is
  meant for Qt4 or 5. Previously this would always install to a path for
  qt5.