WIP: fix for #348, plus compatibility codepath and Pd Vanilla version bump

This fixes a bug with [wrap~] and bumps the version to 0.48 to trigger the new code path.

To my eye the bug looks like a deterministic one. Miller says it's not on his Fedora box. If anyone can explain what would trigger undefined behavior in the old code path I'll remove it entirely.

Also-- we probably need a better process for choosing when to bump Pd Vanilla version number. Here, it's misleading because we haven't added all the other changes from Pd Vanilla. But for this compatibility fix it's the easiest way to do it.