[swift mode] Fix tokenizing of block comments

Closes #6981

Author: marijnh

mode/swift/swift.js

@@ -143,14 +143,12 @@
 
   function tokenComment(stream, state) {
     var ch
-    while (true) {
-      stream.match(/^[^/*]+/, true)
-      ch = stream.next()
-      if (!ch) break
+    while (ch = stream.next()) {
       if (ch === "/" && stream.eat("*")) {
         state.tokenize.push(tokenComment)
       } else if (ch === "*" && stream.eat("/")) {
         state.tokenize.pop()
+        break
       }
     }
     return "comment"