ProfileData: Avoid UB when reading

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206674 91177308-0d34-0410-b5e6-96231b3b80d8
OnDiskHashTable: Audit types and use offset_type consistently

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206675 91177308-0d34-0410-b5e6-96231b3b80d8