first step: compute the shape of the current env

store it in the AST where needed. So far the ConsEnv also still stores
it, but already a sanity check is done on it.
compute and pass the env_structure in assign_convert
some immutable fields
Merge branch 'master' into remove-consenv-args

Conflicts:
	pycket/interpreter.py
fully remove the args from the ConsEnv
only start jitting at likely non-primitive calls

it only checks whether the operator is not directly a primitive name, so
it's a flawed heuristic, but helps a lot.
Merge branch 'master' into remove-consenv-args
Merge branch 'master' into remove-consenv-args

Conflicts:
	pycket/interpreter.py
a docstring, a cleanup
just write a for loop
writing is unroll_safe as well
even different entering: enter at start of function

(kind of obvious, actually, and works great)
Lambdas are simple expression.
Merge remote-tracking branch 'origin/remove-consenv-args' into let-values
fix floor
fix floor
Merge branch 'let-values'

Conflicts:
	pycket/interpreter.py
Fix import.