buildsys: decouple unrelated side effects from $(USE_GTK).
libaudqt: add buildsys scaffolding
configure: add Qt5Gui module to dependencies
configure: also add qt5 widgets module
libaudqt: about window implementation
libaudqt/about: avoid strdup(2) usage
libaudqt: add a utility function to bring any window to the front
Merge pull request #19 from kaniini/master

initial libaudqt work