The typo got unnoticed because we were testing only on Dwarf 2. Add a
Dwarf4 test that exercises the code path, and also tests some newer
FORMs that the other test doesn't cover.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232191 91177308-0d34-0410-b5e6-96231b3b80d8