CORE-10495 CORE-13672
- Fix the behaviour of the EXIT command, where it set the last errorlevel
value ONLY when it was called with the /b switch and otherwise kept the
ambient one, instead of always using the value that the user specified
on the command-line.
- When a batch file has terminated, make the Batch() helper returning the
errorlevel value so that, when the batch file has been started with the
CALL command, CALL can in turn set the correct errorlevel value.
Verified with respect to Windows' cmd.exe.