Add llvm::enumerate() range adapter.

This allows you to enumerate over a range using a range-based
for while the return type contains the index of the enumeration.

Differential revision: https://reviews.llvm.org/D25124

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283337 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed