fixed return type from object to a reference

git-svn-id: svn://bind10.isc.org/svn/bind10/trunk@1313 e5f2f494-b856-4b98-b285-d166d9295462

src/lib/dns/base64.cc

@@ -114,7 +114,7 @@ public:
         }
         return (*this);
     }
-    const char operator*() const {
+    const char& operator*() const {
         if (in_pad_ && *base_ == BASE64_PADDING_CHAR) {
             return (BASE64_ZERO_CODE);
         } else {