This is the fourth part for Analog Devices Blackfin processor, which 
adds the Blackfin simulator. It was written by Bernd Schmidt 
<bernd.schmidt@analog.com>. I cleaned up the source code for submitting.

It's mainly used for GCC testing. Not all Blackfin instructions have 
been implemented. More instructions will be added in future if required.

The sim/bfin/configure is not included in this patch. I'll generate it
from sim/bfin/configure.ac when committing.

Any comments?

Thanks,
Jie