Previously this was a module-level setting, meaning that all REPL instances
had to share the same writer function. Turning it into one of the options
allows individual REPL instances to use their own writer function.
The overall goal here is to make readline more interoperable with other node
Streams like say a net.Socket instance, in "terminal" mode.
See #2922 for all the details.
Closes #2922.
Fix #1484
Fix #1834
Fix #1482
Fix #771
It's been a while now, and we've seen how this separate context thing
works. It constantly confuses people, and no one actually uses '.clear'
anyway, so the benefit of that feature does not justify the constant
WTFery.
This makes repl.context actually be a getter that returns the global
object, and prints a deprecation warning. The '.clear' command is gone,
and will report that it's an invalid repl keyword. Tests updated to
allow the require, module, and exports globals, which are still
available in the repl just like they were before, by making them global.
