For same src/dest don't overwrite file if line endings already normalized.

If the src and dest are the same, updating files even when line endings are already normalized, has undesirable side effects. Among other things, it triggers watch, causes IDE to reload and flush undo/redo history, modifies mtime which is relied for cache busting, etc.

It is fairly common use-case to normalize the files in-place using options:
```
…
src: ['foo/*'],
rename: function(dest, src) {
  return src;
},
…
```