Had a bug with structs that ended up causing many other bugs.
Essentially, was having difficulty copying user-defined structs when
passing them through message sequences.  This was because, I was
holding Waldo-wrapped values of value types instead of the value types
themselves.  (Which meant that on copy, I was passing around external
references.)  Fixed this by removing the Waldo-wrapping from internal
objects.  However, functions still need wrapping (so can keep track of
external args).