add isnan

stl/lib.nas

@@ -138,7 +138,9 @@ var math=
     exp:   func(x)  {return __builtin_exp(x);    }, 
     ln:    func(x)  {return __builtin_ln(x);     },
     sqrt:  func(x)  {return __builtin_sqrt(x);   },
-    atan2: func(x,y){return __builtin_atan2(x,y);}
+    atan2: func(x,y){return __builtin_atan2(x,y);},
+    nan:   func()   {return 1/0-1/0;             },
+    isnan: func(x)  {return __builtin_isnan(x);  }
 };
 
 var D2R=math.pi/180;