freja-dofile should handle removal of old symbols

[saikyun]

There are two alternatives for freja-dofile:

Use an existing env when running dofile

Benefits:

• Simple due to no need to handle defonce and vars in a special way

Drawbacks:

• Can mess up existing env with no recovery

Use a new env when running dofile

Benefits:

• Cleaner, won't mess with existing env while compiling / evaling

Drawbacks:

• Trickier to get vars and defonce working

Current state

Having some problems with vars working with second way. Might have figured out defonces.