Silence unused variable and parameter warnings.


git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@211790 91177308-0d34-0410-b5e6-96231b3b80d8
Silence the implicit signed/unsigned conversion warning.


git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@211912 91177308-0d34-0410-b5e6-96231b3b80d8