[ARM] Add pre-defined macros for ROPI and RWPI

This adds ACLE-defined macros to test for code being compiled in the ROPI and
RWPI position-independence modes.

Differential revision: https://reviews.llvm.org/D23610



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@354265 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed