Sort includes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210613 91177308-0d34-0410-b5e6-96231b3b80d8
Move to a private function to initialize the subtarget dependencies
so that we can use initializer lists for the X86Subtarget.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210614 91177308-0d34-0410-b5e6-96231b3b80d8