[clang-move] Add some options allowing to add old/new.h to new/old.h respectively.

Summary:
* --new_depend_on_old: new header will include old header
* --old_depend_on_new: old header will include new header.

Reviewers: ioeric

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D26966

llvm-svn: 287752