add RWFifo for debugging
throw exception instead of aborting the process when called from python
enable exceptions (instead of abort) in C code

This is better than doing it in ex_utils.py because it will work
before a SimulavrAdapter instance is created. I also like that
this code is next to the code that handles these exceptions.
add dependency tracking for swig build
bugfix: nodirector cannot be set on a class that has a director method
add verbose option for RWFifo

You must also enable verbose output for simulavr:
pysimulavr.cvar.global_verbose_on = True