Fix LXQT-9999 Build Failures

* lxqt now requires qtmimetypes library to compile
* New Ebuild for qtmimetypes
* Patch for build failures in lxqt-config
* Add dependency qtmimetypes use flag in libqtxdg in order to build
  liblxqt and lxqt-panel packages
  Note: razor-qt does not require the qtmimetypes use flag (yet)
i tested builds on qt4 which is where qtmimetypes is relevant, so to answer you question, when qt5 is used no you don't need qtmimetypes.. also the libqtxdg build  will fail if you attempt qt5 and qtmimetypes