superbol-debug: function breakpoints don't work

[GitMensch]

I've added both a C function breakpoint "cob_stop_run" and a COBOL one "PROG2" (which is, of course, CALLed from the main program); neither worked (the program executed without waiting)

[nberth]

Calls on the COBOL side should be fixed by #454. Support for C-side breakpoints needs to be tested again.