debugging: save attributed string as XML property list

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
fix useage of [f descender] (usually returns negative value!)

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
updated .xcodeproj for Xcode 6.1

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>