TMS57002 fixes and improvements: [Phil Bennett]
 - Moved CA/ID post-increment outside of execution.
   Fixes case where dual instructions post-increment, also reduces number of generated instructions.
 - Fixed data ordering of external memory accesses.
 - Don't generate redundant instructions for undefined rounding modes; remap them in decode.
 - Set XOA to 0 on reset.
 - Use [READ|WRITE]LINE_MEMBER for I/O lines.
 - Added PC0 line.
 - Added registers to debugger state.