Amended - Make the REPL *CLI* use the global context so as to be consistent with the `node` REPL CLI.

(My apologies: In the previous commit I accidentally made `useGlobal:
yes` the default for _programmatic_ use also, but the intent was to
only do it for the stand-alone *CLI*.)

Make the REPL *CLI* use the global context so as to (a) be consistent
with the `node` REPL CLI and, therefore, (b) make packages that modify
native prototypes (such as 'colors' and 'sugar') work as expected.

Note that, by contrast, programmatic use (`require 'repl'`) will
continue to default to a NON-global context - again, consistent with
node's behavior.