Add proper headers in CFGUpdate.h and add CFGDiff.h in the list of delayed...

Add proper headers in CFGUpdate.h and add CFGDiff.h in the list of delayed headers for LLVM_intrinsic_gen.

Summary:
Fix module build after r339694.
Add headers needed in CFGUpdate.h.
Add CFGDiff.h in the list of delayed headers for LLVM_intrinsic_gen.
Up for post-commit review.

Subscribers: sanjoy, jlebar, llvm-commits

Differential Revision: https://reviews.llvm.org/D50734

llvm-svn: 339724