[src/core/Numeric.pm] made NaN ~~ NaN true

Borrowed the implementation from Beijing.

src/core/Numeric.pm

@@ -2,7 +2,9 @@
 my class Numeric {
     multi method Numeric(Numeric:D:) { self }
 
-    multi method ACCEPTS(Numeric:D: $a) { $a == self }
+    multi method ACCEPTS(Numeric:D: $a) {
+        self.isNaN ?? $a.isNaN !! $a == self;
+    }
 
     proto method log(|$) {*}
     multi method log(Cool    $base) { self.log / $base.Numeric.log }