* Exit with an error message when the option is not a node or V8 option.
* Remove the option_end_index global. Needs to happen anyway for
the multi-context work, might as well land it in master now.
* Add a smidgen of const-correctness.
* Pay off a few years of accrued technical debt.
The test checked that stdout was empty. Forgetting to escape brackets
in the argument to --eval made that true on UNIX systems: the error
was written to stderr.
Props to Peter Bright for reporting the issue.