When aborting due to unknown opcode, output more descriptive msg
-------------------- ChangeLog entries follow: --------------------
src/ChangeLog addition:
2010-02-02 Ben Wing <ben@xemacs.org>
* bytecode.c (execute_rare_opcode):
* lisp.h (abort_with_msg): New.
When aborting due to unknown opcode, output more descriptive msg.