'Change Instrument' doesn't respect font style for InstrumentLong and InstrumentShort

This seems to be a revived #1754: Instrument names use wrong font (regression). The problem has been mentioned in http://musescore.org/node/4569#comment-12119.

STR:
1. run the 'Create Score' plugin
2. from the staff context menu ('Staff Properties' / 'Part Properties' / 'Change Instrument') switch the instrument from piano to harp.

Actual results: InstrumentLong (InstrumentShort is set only when there is a line break in the score) uses the "Application Font" as set in 'Preferences' / 'General'.

Expected results: InstrumentLong uses the corresponding default style as set in 'Style' / 'Edit Text Style'.

MuseScore r2796 on Ubuntu 9.10 with Qt 4.6.1