Make test/Driver hermetic

Summary:
The includes shouldn't be there, use the compiler's built-in types/macros instead.

This is a follow-up to r217694, as discussed in:
  http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20140908/114669.html

Test Plan: ninja check-clang

Reviewers: nlewycky, thakis, echristo, chandlerc

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D5348

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@217743 91177308-0d34-0410-b5e6-96231b3b80d8