repl: Add paste mode to friendly REPL, entered via CTRL-E.
Use CTRL-E to enter paste mode. Prompt starts with "===" and accepts all characters verbatim, echoing them back. Only control characters are CTRL-C which cancels the input and returns to normal REPL, and CTRL-D which ends the input and executes it. The input is executed as though it were a file. The input is not added to the prompt history.