libopensc: avoid call to memset() with zero length
libopensc: avoid call to memset() with zero length

@mouse07410 has asked for it in
https://github.com/OpenSC/OpenSC/issues/688#issuecomment-219433611

VTA: I do not see the difference (if the other arguments are properly used),
but assume that @mouse07410 has it's own valid reasons

Also included the few coding style touches.

fabled/OpenSC,rickyepoderi/OpenSC,CardContact/OpenSC,viktorTarasov/OpenSC-SM,OpenSC/OpenSC,philipWendland/OpenSC,nmav/OpenSC,LudovicRousseau/OpenSC,nmav/OpenSC,philipWendland/OpenSC,dengert/OpenSC,frankmorgner/OpenSC,fabled/OpenSC,martinpaljak/OpenSC,OpenSC/OpenSC,dengert/OpenSC,LudovicRousseau/OpenSC,martinpaljak/OpenSC,mouse07410/OpenSC,martinpaljak/OpenSC,frankmorgner/OpenSC,mouse07410/OpenSC,nmav/OpenSC,rickyepoderi/OpenSC,frankmorgner/OpenSC,mtrojnar/OpenSC,jpki/OpenSC,hongquan/OpenSC-main,OpenSC/OpenSC,metsma/OpenSC,mtrojnar/OpenSC,philipWendland/OpenSC,fabled/OpenSC,AktivCo/OpenSC,Jakuje/OpenSC,dengert/OpenSC,jpki/OpenSC,viktorTarasov/OpenSC-SM,mouse07410/OpenSC,CardContact/OpenSC,AktivCo/OpenSC,Jakuje/OpenSC,jpki/OpenSC,hongquan/OpenSC-main,hhonkanen/OpenSC,hongquan/OpenSC-main,AktivCo/OpenSC,Jakuje/OpenSC,metsma/OpenSC,metsma/OpenSC,hhonkanen/OpenSC,mtrojnar/OpenSC,fabled/OpenSC,hhonkanen/OpenSC,viktorTarasov/OpenSC-SM,CardContact/OpenSC,rickyepoderi/OpenSC,Jakuje/OpenSC,LudovicRousseau/OpenSC,frankmorgner/OpenSC