Many .desktop files adjusted. Slackbuilds updated.

For .desktops:
hydrogen
audacity
denemo
mscore
rosegarden
jack-rack
rakarrack
frescobaldi
SimpleSexxer
mixxx
ardour and (3)
jokosher
qtractor
calf
lv2
timemachine
giada
sooperlooper
specimen
muse
seq24
amsynth
pd
qsynth
sunvox
qjackctl
Other:
muse doinst.sh fixed for setcap
ardour sqf order (and 3)
calf for deps and configure options
lv2 SLAKCFLAGS