Correctly export _Unwind_[GS]et(GR|IP) for EHABI.

These need to have normal linkage instead of being static inline as
many libraries expect to be able to declare these and have the linker
find them rather than needing to include the header.

http://mentorembedded.github.io/cxx-abi/abi-eh.html

Also clean up some warnings while I'm here.

Reviewers: jroelofs, kledzik

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D5754


git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@219629 91177308-0d34-0410-b5e6-96231b3b80d8