Previously introduced node comparison `==` was working somehow wrong on nodes
returned from getType(a), comparing just ids of the symbols.
Recently introduced `==` change 47dce26886
started comparing symbol nodes pointer-wise, thus strictly. Since getType(a)
always creates new symbol pointing to the type, comparing two such nodes using
`==` always returns false, even they point to the same type.
That is why we need a new sameType macro to be able to tell if these nodes
point to the same type.
