Fix XdgDirs::dataDirs() postfix handling
Fix XdgDirs::dataDirs() postfix handling

The postfix was being appended to the dir list instead of being
concatenated to the dir list entries.

libqtxdg/libqtxdg,luis-pereira/libqtxdg,DrTobe/libqtxdg,lxde/libqtxdg,lxde/libqtxdg,luis-pereira/libqtxdg,libqtxdg/libqtxdg,DrTobe/libqtxdg,DrTobe/libqtxdg