Base profile: unmask newer Phonon, required to build against musl

profiles/base/package.accept_keywords

@@ -2,6 +2,7 @@
 =app-arch/pax-20160306 **
 =app-eselect/eselect-timezone-0.2 **
 =dev-util/cflow-1.4 **
+=media-libs/phonon-4.9.0 **
 =sys-apps/less-483-r1 **
 =sys-apps/shadow-4.2.1-r2 **
 =sys-devel/gcc-5.4.0 **