Execute a sub process with some more options (EXPERIMENTAL)
[sim, out] = ld_startproc2(sim, events, exepath, chpwd, prio, whentorun)
out * - output
exepath - string: path to executable
chpwn - change current directory before running the process
prio - Priority (set to zero for now)
whentorun - 0 - Start process on blocks initialisation and stop on desruction;
1 - Start process on activation in a statemachine and stop on reset