Fix a build problem with xlc. The error message was

"../llvm-git/utils/TableGen/CodeGenSchedule.cpp", line 1594.12: 1540-0218 (S) The call does not match any parameter list for "operator+".
"../llvm-git/include/llvm/ADT/STLExtras.h", line 130.1: 1540-1283 (I) "template <class _Iterator, class Func> llvm::operator+(mapped_iterator<_Iterator,Func>::difference_type, const mapped_iterator<_Iterator,Func> &)" is not a viable candidate.

Patch by Kai.

llvm-svn: 167311