proc-val-ref now becomes uninitalized once it's done being used.
Merge branch 'master' into belt-and-suspenders
shifts letrec specific GC to own function

fixes issue where non-letrec function calls would throw
an error

Exception occured in vector-set!:  uninitialized is not a valid index
for (store)
Merge branch 'master' into belt-and-suspenders