Verifier: Check operands of MDType subclasses and MDCompileUnit

Add verify checks for `MDType` subclasses and for `MDCompileUnit`.
These new checks don't yet incorporate everything from `Verify()`, but
at least they sanity check the operands.  Also downcast accessors as
possible.

A lot of these accessors can't be downcast as far as we'd like because
of arrays of typed objects (stored in a generic `MDTuple`) and
`MDString`-based type references.  Eventually I'll port over `DIRef<>`
and `DITypedArray<>` from `DebugInfo.h` to clean those up as well.

Updated bitrotted testcases separately in r233415 and r233443 to reduce
churn on the off-chance this needs to be reverted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233446 91177308-0d34-0410-b5e6-96231b3b80d8

lib/IR/DIBuilder.cpp

@@ -269,8 +269,8 @@ DIDerivedType DIBuilder::createReferenceType(unsigned Tag, DIType RTy) {
 
 DIDerivedType DIBuilder::createTypedef(DIType Ty, StringRef Name, DIFile File,
                                        unsigned LineNo, DIDescriptor Context) {
-  return MDDerivedType::get(VMContext, dwarf::DW_TAG_typedef, Name,
-                            File.getFileNode(), LineNo,
+  return MDDerivedType::get(VMContext, dwarf::DW_TAG_typedef, Name, File,
+                            LineNo,
                             DIScope(getNonCompileUnitScope(Context)).getRef(),
                             Ty.getRef(), 0, 0, 0, 0);
 }