$ ); echo $? echoed 0,all other shells echo 2.

$ ); echo $? echoed 0,all other shells echo 2.
Now we set the exitstatus to 2 for all EXERROR errors.
Also I changed the exitstatus to 1 when a command is not found
to comply with historical practice.

SCCS-vsn: bin/sh/main.c 8.5
SCCS-vsn: bin/sh/eval.c 8.8