repl: make REPLServer inherit from EventEmitter
repl: make REPLServer inherit from EventEmitter

This is because it should emit an "exit" event when "SIGINT" is received
from the readline interface, or when ".exit" is typed by the user.

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node