I messed up the nprocesses/nthreads parameter

for linking against some particular libraries, it's necessary to add
"extra_libraries" such as '-Wl,--start-group'.
Therefore when the compile command is now constructed, "extra_libraries"
are checked to see whether they start with '-' or '/' (for static
libraries given as full file names).

incidentally, it looks like the binary reader is working.

make sure code stops at multiples of niter_todo, or when
the file "stop_<simname>" is found.
i.e. if i stop it at iteration 3, and niter_todo is 16, it should next
stop at 16, not at 19.

the mechanism seems to be working ok, I still need to implement a "STOP"
command of some sort.