Add some uncommitted stuff to TODO.

Timestamp indicates that these additions were written around Jun 6 2011.
Improvements to write-rust-bytecode.js.

Better rust-style string escaping.  Note that rust uses UCS4 while
JavaScript uses UTF16.  We have to do a bit of conversion as we write
strings.

See https://github.com/cscott/rusty-turtle for the project which uses
the output of write-rust-*.js