Support general comment blocks in addition to line comments

The tool only supports line comments at this time. Additionally, it will not detect existing general comment blocks, causing duplication where these have been used.

Example diff:

```
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
/*

Licensed under the Apache License, Version 2.0 (the "License");
```