opensc-explorer: refactor read_cmdline()
opensc-explorer: refactor read_cmdline()

* add comments
* simplify #ifdef logic
* increase commandline buffer in non-interactive / non-readline case

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