JavaScript: uniform usage of _dumps.
Cleanup.
Notes about serialization exceptions/examples.
Add a graceful BYE token to detect repl termination.
PHP: correctly unwind the stack on serialization errors with exported functions.
Optimize the main repl.
Python: force an interactive prompt.
Switch the terminal in raw mode as soon as the remote REPL is ready.

- This avoids buffer overflows in pty's line discipline.
- The line discipline might still need to be turned off remotely...