GC Improvement

[JM4ier]

Currently the GC searches through the whole stack and checks if integers could be references to lisp values.
If it thinks it could be a reference to one, it doesn't garbage collect that value.

Since the references are indices into the lisp memory buffer, the values are rather small.
It is possible that the GC finds a lot of false positive references.

It could be of interest to store references to lisp values in a slightly different way so false positives are minimized.

[JM4ier]

An alternative (and probably easier) way would be to run a slightly modified GC at the top level in between interpreting clauses.
That way, there should be no references on the stack and no false positives can occur.