objects: Add equality for BoolObjects and CharObjects.
Handle assignment.
env: Annotate nodes with final/var information.

Prevents accidental updates of otherwise-final names during assignment.

For the first time, we now have enough code to make an entire line of
Mandelbrot during annotation! Whoo!
objects: Add slice/1 to StrObjects.
nodes: Create new scopes for If and Finally.

Open question: How does Finally share its scopes?
Fix translation.