Summary:

Object: add IMAGE_FILE_MACHINE_ARM64

The official specifications state that the value of IMAGE_FILE_MACHINE_ARM64
is 0xAA64 (as per the Microsoft Portable Executable and Common Object Format
Specification v8.3).

Reviewers: rnk

Subscribers: llvm-commits, compnerd, ruiu

Differential Revision: http://reviews.llvm.org/D11511

llvm-svn: 243434