Fixed mhical(1) exit status to reflect return status of icalparse().

Fixed mhical(1) exit status to reflect return status of icalparse().

Also, removed parser_status as a global:  just use the return status
of icalparse().  And had to change test-mhical to reflect new exit
status from mhical with empty input.

Thanks to Ralph for pointing out that test-mhical previously had an
unnecessary test of the mhical exit status.