doc/error.md: static errors are also programming errors
Implement closure enclosure.

Scopes are now represented by map[string]*Value instead of map[string]Value,
allowing multiple scopes to share the same Value instance.
Cross static checker and closure capturing off TODO list
Clarify an item about error handling in TODO
Implement StreamType inference for closures; print closures with %v
New editor builtin kill-word-left
Makefile: Remove gofmt goal
eval: A little moving around...
eval: Variables now have static types
eval: Utilize closure annotation to determine form annotation
eval: Fix ClosureType.Default
eval: Remove an XXX regarding enclosed variables
eval: resolveCommand now uses closure type info