python: Add support for debugging
python: Print debug information on demand
python: Catch jumps pushed more than once

I'm diagnosing a problem running tests/rot13.bf. This may help.
python: Dump debug info when exception occurs
python: Print current cell value with debug info
Revert "python: Catch jumps pushed more than once"

This reverts commit 349398fd3b48c4a86d1e1f64af81aa6e1d445d07.
python: Only pop jump value if not repeating loop
python: Only append jump if not already in jump list
c: Implement algorithm changes from Python implementation
objc: Implement algorithm changes from Python implementation