=== should fail if not identical types

http://irclog.perlgeek.de/perl6/2016-04-19#i_12363756

This breaks some spectests.  Since we're just after the release, I'm
going to leave them for now, hoping someone else will look at the
failures.

src/core/Any.pm

@@ -425,8 +425,11 @@ Metamodel::ClassHOW.exclude_parent(Any);
 # builtin ops
 proto sub infix:<===>(Mu $?, Mu $?) is pure { * }
 multi sub infix:<===>($?)    { Bool::True }
-multi sub infix:<===>($a, $b) {
-    nqp::p6bool(nqp::iseq_s(nqp::unbox_s($a.WHICH), nqp::unbox_s($b.WHICH)))
+multi sub infix:<===>(\a, \b) {
+    nqp::p6bool(
+      nqp::eqaddr(a.WHAT,b.WHAT)
+      && nqp::iseq_s(nqp::unbox_s(a.WHICH), nqp::unbox_s(b.WHICH))
+    )
 }
 
 proto sub infix:<before>(Mu $?, Mu $?)  is pure { * }

src/core/Int.pm

@@ -284,7 +284,10 @@ multi sub infix:<gcd>(int $a, int $b) returns int {
 }
 
 multi sub infix:<===>(Int:D \a, Int:D \b) {
-    a.WHAT =:= b.WHAT && nqp::p6bool(nqp::iseq_I(nqp::decont(a), nqp::decont(b)))
+    nqp::p6bool(
+      nqp::eqaddr(a.WHAT,b.WHAT)
+      && nqp::iseq_I(nqp::decont(a), nqp::decont(b))
+    )
 }
 multi sub infix:<===>(int $a, int $b) {
     # hey, the optimizer is smart enough to figure that one out for us, no?

src/core/Num.pm

@@ -383,7 +383,10 @@ multi sub infix:«<=>»(num $a, num $b) {
 }
 
 multi sub infix:<===>(Num:D \a, Num:D \b) {
-    a.WHAT =:= b.WHAT && nqp::p6bool(nqp::iseq_n(nqp::unbox_n(a), nqp::unbox_n(b)))
+    nqp::p6bool(
+      nqp::eqaddr(a.WHAT,b.WHAT)
+      && nqp::iseq_n(nqp::unbox_n(a), nqp::unbox_n(b))
+    )
 }
 multi sub infix:<===>(NaN, NaN) {
     True;

src/core/Str.pm

@@ -1858,7 +1858,10 @@ multi sub infix:<cmp>(str $a, str $b) returns Order:D {
 }
 
 multi sub infix:<===>(Str:D \a, Str:D \b) returns Bool:D {
-    nqp::p6bool(nqp::iseq_s(nqp::unbox_s(a), nqp::unbox_s(b)))
+    nqp::p6bool(
+      nqp::eqaddr(a.WHAT,b.WHAT)
+      && nqp::iseq_s(nqp::unbox_s(a), nqp::unbox_s(b))
+    )
 }
 multi sub infix:<===>(str $a, str $b) returns Bool:D {
     nqp::p6bool(nqp::iseq_s($a, $b))