It was arbitrary that this struct had it and not dozens of others.

Older C++ doesn't allow struct-with-constructor in union.

Newer compilers / language allows structs with constructor in union.
So, this was not actually testing anything.  Indeed, the recent
change in DISALLOW_COPY *is* making some of our types non-POD.
That broke some bots.

Just remove this since it wasn't doing much, and I'd rather have
DISALLOW_COPY.

Finally!  Catches hard-to-find errors like this:

-    const SortedArrayOf<SVGDocumentIndexEntry> docs = this+svgDocEntries;
+    const SortedArrayOf<SVGDocumentIndexEntry> &docs = this+svgDocEntries;

We implement this for our array types.  This, in turn, trickles down
into all types that embed the arrays.  So, as long as we define all
open-ended structs in terms of Array types (all can be done using
UnsizedArrayOf), this achieves the goal of making uncopyable all
structs that are variable-sized.  Yay!

Revive and rename dump-emoji to test-ot-color but use public APIs instead

If struct members are simple and needed publicly, we make them public.