This change cleans up warnings issued when compiled with
-Wall.
- Removed unused functions and variables.
- Moved static declarations out of headers and into source files
- Added braces around initialization where suggested.
Adds a skeleton framework for CIO ("Common I/O") feature cards. The
first feature card to be implemented will be the "PORTS" serial MUX.
Part of this support involved reworking IRQ handling in the CPU. It
now respects both IRQ Vector and IPL.
This change also removes all 'assert(0)' calls from the simulator and
replaces them with generic "Simulator Error" halts. These should only
happen if there's a genuine logic error lurking somewhere.
