In typeCallInternal, we used to expand out any starargs in order to take a look
at the first arg (and change it when passing it).

We had a bug in this code, and rather than make that code more complicated
to fix it, just call back into callFunc to resolve it.  This is kind of tricky
since callFunc will call typeCall, and we don't want typeCall to duplicate
the typeCallInternal behavior (that's not any better than duplicating the
arg behavior), so we want typeCall to call into typeCallInternal.  But
typeCall receives varargs! which typeCallInternal doesn't support.  So typeCall
has to do some (simpler) arg handling to expand out the varargs.

In the end, it simplifies the code a little bit but causes a bunch of extra calls
in the varargs case, so it's less of a win than I thought, but at least it
fixes the bug.