[clang-move] Clever on handling header file which includes itself.

Summary:
Previously, we assume only old.cc includes "old.h", which would
introduce incorrect fixes for the cases where old.h also includes `#include "old.h"`

Although it should not be occurred in real projects, clang-move should handle this.

Old.h:

```
class Foo {};
```

after moving to a new old.h:

```
class Foo {};
```

Reviewers: ioeric

Reviewed By: ioeric

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D42639

llvm-svn: 323865