mark_overlays: Use the normal ITREE_FOREACH

This commit basically reverts commit 5b954f8f9.  The problem of nested
iterations hasn't been fixed in the mean time, but since the GC can
run arbitrary ELisp code (via `post-gc-hook`), running the GC from
within an itree iteration is already unsafe anyway :-(

* src/alloc.c (mark_overlays): Delete function.
(mark_buffer): Use ITREE_FOREACH.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/itree.h b/src/itree.h
index 1f019a2607e..29bc8dd1b25 100644
--- a/src/itree.h
+++ b/src/itree.h
@@ -105,7 +105,8 @@ void interval_tree_delete_gap (struct interval_tree *, ptrdiff_t, ptrdiff_t);
    - The expression T may be evaluated more than once, so make sure
      it is cheap a pure.
    - Only a single iteration can happen at a time, so make sure none of the
-     code within the loop can start another tree_itertion.
+     code within the loop can start another tree iteration, i.e. it shouldn't
+     be able to run ELisp code (or GC for that matter).
    - If you need to exit the loop early, you *have* to call `ITREE_ABORT`
      just before exiting (e.g. with `break` or `return`).
    - Non-local exits are not supported within the body of the loop,