We currently use -1 as default value for resources
when the actual value is not available.
-1 is good for fd's, but is not the right default
value for pointers/keys/etc.
Pass from prog and use in executor proper default
value for resources.
Generated program always uses pid=0 even when there are multiple processes.
Make each process use own pid.
Unfortunately required to do quite significant changes to prog,
because the current format only supported fixed pid.
Fixes#490
Factor out program parsing from pkg/csource.
csource code that parses program and at the same time
formats output is very messy and complex.
New aproach also allows to understand e.g.
when a call has copyout instructions which is
useful for better C source output.
