Fix some memory leaks

src/stack.c

@@ -26,6 +26,21 @@ void lisp_init_stack(void) {
     the_stack.nogc_retval = Qnil;
 }
 
+static void teardown_stack_frame(struct StackFrame *restrict frame) {
+    for (size_t i = 0; i < frame->local_refs.num_blocks; ++i) {
+        lisp_free(frame->local_refs.blocks[i]);
+    }
+    lisp_free(frame->local_refs.blocks);
+}
+
+void lisp_teardown_stack(void) {
+    assert(the_stack.depth == 0);
+    for (size_t i = 0; i < the_stack.max_depth; ++i) {
+        teardown_stack_frame(&the_stack.frames[i]);
+    }
+    lisp_free(the_stack.frames);
+}
+
 void push_stack_frame(LispVal *name, LispVal *fobj, LispVal *args) {
     assert(the_stack.depth < the_stack.max_depth);
     struct StackFrame *frame = &the_stack.frames[the_stack.depth++];
@@ -164,6 +179,7 @@ void add_local_reference(LispVal *obj) {
     while ((cur = next_local_reference(&i))) {
         add_local_refs_for_object_sub_vals(seen_objs, cur);
     }
+    release_hash_table_no_gc(seen_objs);
 }
 
 void compact_stack_frame(struct StackFrame *restrict frame) {