Restructure the code in copyfuncs and equalfuncs to put much heavier

reliance on macros, in hopes of eliminating silly typos (like copying
to the wrong field) and just generally making it easier to see the forest
instead of the trees.  As an example, here is the new code for A_Indices:

static A_Indices *
_copyAIndices(A_Indices *from)
{
	A_Indices  *newnode = makeNode(A_Indices);

	COPY_NODE_FIELD(lidx);
	COPY_NODE_FIELD(uidx);

	return newnode;
}

static bool
_equalAIndices(A_Indices *a, A_Indices *b)
{
	COMPARE_NODE_FIELD(lidx);
	COMPARE_NODE_FIELD(uidx);

	return true;
}

I plan to redo outfuncs/readfuncs in a similar style, but am committing
what I've got.