testing/*: rebuild against libxml2

testing/apt-dater/APKBUILD

testing/aravis/APKBUILD

testing/armagetronad/APKBUILD

testing/certmonger/APKBUILD

testing/cluster-glue/APKBUILD

testing/createrepo_c/APKBUILD

testing/dnsperf/APKBUILD

testing/electron/APKBUILD

testing/elementary-photos/APKBUILD

testing/flowtime/APKBUILD

testing/gpscorrelate/APKBUILD

testing/hiawatha/APKBUILD

testing/hurl/APKBUILD

testing/kannel/APKBUILD

testing/libabigail/APKBUILD

testing/libideviceactivation/APKBUILD

testing/libigraph/APKBUILD

testing/libqb/APKBUILD

testing/libvisio2svg/APKBUILD

testing/libxml++/APKBUILD