More conversions

[russtoku]

Converted clients:

• snd-s7
• Python (with small refinements)
• Scheme
• Hy (not tested)
• Julia (not tested)
• Janet stdio (not tested)
• Fennel stdio

Converted:

• remote/transport/base64
• remote/transport/bencode
• remote/stdio and associated test

Touch up:

• dev/python/sandbox.py
• remote/stdio-rt