make --comments keep @cc_on too

bin/uglifyjs2

@@ -125,8 +125,7 @@ if (ARGS.comments) {
             var type = comment.type;
             if (type == "comment2") {
                 // multiline comment
-                return text.indexOf("@preserve") >= 0
-                    || text.indexOf("@license") >= 0;
+                return /@preserve|@license|@cc_on/i.test(test);
             }
         }
     }

lib/parse.js

@@ -473,14 +473,6 @@ function tokenizer($TEXT, filename) {
             S.pos = i + 2;
             S.line += text.split("\n").length - 1;
             S.newline_before = S.newline_before || text.indexOf("\n") >= 0;
-
-            // https://github.com/mishoo/UglifyJS/issues/#issue/100
-            if (/^@cc_on/i.test(text)) {
-                warn("WARNING: at line " + S.line);
-                warn("*** Found \"conditional comment\": " + text);
-                warn("*** UglifyJS DISCARDS ALL COMMENTS.  This means your code might no longer work properly in Internet Explorer.");
-            }
-
             return token("comment2", text, true);
         });
     };
@@ -1493,5 +1485,3 @@ function parse($TEXT, options) {
     })();
 
 };
-
-var warn = function() {};