Add function for computing the edit distance of two arrays.

Accomplished by moving the body of StringRef::edit_distance into
a separate function that accepts two ArrayRefs, and making
StringRef::edit_distance a wrapper around the new function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150621 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed