Two more definitions required by libsupc++ (_sleb128_t and _uleb128_t)

Differential Revision: http://llvm-reviews.chandlerc.com/D1542

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@189558 91177308-0d34-0410-b5e6-96231b3b80d8