AIX system headers need stdint.h and inttypes.h to be re-enterable

AIX system headers need stdint.h and inttypes.h to be re-enterable

Summary:
AIX system headers need stdint.h and inttypes.h to be re-enterable when macro _STD_TYPES_T is defined so that limit macro definitions such as UINT32_MAX can be found. This patch attempts to allow that on AIX.

Reviewers: hubert.reinterpretcast, jasonliu, mclow.lists, EricWF

Reviewed by: hubert.reinterpretcast, mclow.lists

Subscribers: jfb, jsji, christof, cfe-commits, libcxx-commits, llvm-commits

Tags: #LLVM, #clang, #libc++

Differential Revision: https://reviews.llvm.org/D59253

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@363939 91177308-0d34-0410-b5e6-96231b3b80d8