Okay, NOW correctly handling scope wrt mixins. (If a binding exists then change it, otherwise make a new one in the topmost (i.e., local) environment.)

Extensible environments. More powerful than necessary, but will be necessary if scoped variables and mixins are added to the language.

Basic mixin functionality. Still need to properly implement environment lookup and correct indentation.

No longer doing single-pass parsing/expansion. Building up a queue of pending expansions/evaluations, then performing them after parse. Should combine the efficiency of single-pass with the ease of multi-pass. Small bug that needs fixing.

Rolling back to before I started the delayed-evaluation stuff. Didn't checkout an older commit because I wanted to keep some of the new stuff.