Fingering font weight

[Nick Payne]

If I change the fingering font, how can I get the bold version of the 
selected font to be used. In the example below, overriding the font and 
the font-size works ok, but overriding the font-series to bold doesn't.

\version "2.17.11"

\relative c'' {
<c-3>
\override Fingering.font-name = #'"Arial"
<c-3>
\override Fingering.font-size = #-3
<c-3>
\override Fingering.font-series = #'bold
<c-3>
}

The output of -dshow-available-fonts shows that Arial regular, italic, 
bold, and bold-italic are all there:

family Arial
Arial:style=Bold Italic,Negreta cursiva,tučné kurzíva,fed kursiv,Fett 
Kursiv,Έντονα Πλάγια,Negrita Cursiva,Lihavoitu Kursivoi,Gras 
Italique,Félkövér dőlt,Grassetto Corsivo,Vet Cursief,Halvfet 
Kursiv,Pogrubiona kursywa,Negrito Itálico,Полужирный Курсив,Tučná 
kurzíva,Fet Kursiv,Kalın İtalik,Krepko poševno,nghiêng đậm,Lodi etzana
family Arial
Arial:style=Italic,Cursiva,kurzíva,kursiv,Πλάγια,Kursivoitu,Italique,Dőlt,Corsivo,Cursief,Kursywa,Itálico,Курсив,İtalik,Poševno,nghiêng,Etzana
family Arial
Arial:style=Regular,Normal,obyčejné,Standard,Κανονικά,Normaali,Normál,Normale,Standaard,Normalny,Обычный,Normálne,Navadno,thường,Arrunta
family Arial
Arial:style=Bold,Negreta,tučné,fed,Fett,Έντονα,Negrita,Lihavoitu,Gras,Félkövér,Grassetto,Vet,Halvfet,Pogrubiony,Negrito,Полужирный,Fet,Kalın,Krepko,đậm,Lodia