This is part XVI of cmd engine rewrite.
Nothing fancy, mainly setting success/failure return code for a bunch of commands. Some code cleanup.
-- v2: programs/cmd: Set success/failure return code for LABEL command. programs/cmd: Set success/failure return code for VOL command. programs/cmd: Set success/failure return code for VERIFY command. programs/cmd: Set success/failure return code for VER command. programs/cmd: Set success/failure return code for DATE TIME commands. programs/cmd: Set success/failure return code for SETLOCAL/ENDLOCAL commands. programs/cmd/tests: Test success / failure for more commands.