v68k-callbacks:  Add chk_trap and trapv_trap
x68k:  Handle CHK and TRAPV exceptions
v68k-callbacks:  Add trace_exception_callback()
x68k:  Handle Trace exceptions
v68k-callbacks:  Add line_A_emulator_callback()
xv68k:  Report unimplemented system calls
v68k-callbacks:  Add _BlockMove trap callback
xv68k:  Set _BlockMove address to native callback
Merge branch 'v68k-things'