macros: Introduce sameType(a, b) for node types

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.

compiler/vm.nim

@@ -692,6 +692,9 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
       regs[ra].intVal =
         ord(exprStructuralEquivalent(regs[rb].node, regs[rc].node,
                                      strictSymEquality=true))
+    of opcSameNodeType:
+      decodeBC(rkInt)
+      regs[ra].intVal = ord(regs[rb].node.typ.sameTypeOrNil regs[rc].node.typ)
     of opcXor:
       decodeBC(rkInt)
       regs[ra].intVal = ord(regs[rb].intVal != regs[rc].intVal)