Fix #597

NaN and Infinity were replaced in the output generation, instead of
during compression. This could lead to results where `1/0` was inserted
without parens leading to invalid output.

The nodes are replaced in the compression step now, and the output
generation returns their regular names. This should not be a problem,
since they're already only constructed from the original name.

lib/output.js

@@ -549,12 +549,6 @@ function OutputStream(options) {
             return true;
     });
 
-    PARENS(AST_NaN, function(output){
-        var p = output.parent();
-        if (p instanceof AST_PropAccess && p.expression === this)
-            return true;
-    });
-
     PARENS([ AST_Assign, AST_Conditional ], function (output){
         var p = output.parent();
         // !(a = false) → true
@@ -1109,10 +1103,10 @@ function OutputStream(options) {
     });
     DEFPRINT(AST_Hole, noop);
     DEFPRINT(AST_Infinity, function(self, output){
-        output.print("1/0");
+        output.print("Infinity");
     });
     DEFPRINT(AST_NaN, function(self, output){
-        output.print("0/0");
+        output.print("NaN");
     });
     DEFPRINT(AST_This, function(self, output){
         output.print("this");