Rewrite #includes for llvm/Foo.h to llvm/IR/Foo.h as appropriate to
reflect the migration in r171366.

Re-sort the #include lines to reflect the new paths.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171369 91177308-0d34-0410-b5e6-96231b3b80d8