DI/Verifier: Fix argument bitrot in DILocalVariable

Add a verifier check that `DILocalVariable`s of tag
`DW_TAG_arg_variable` always have a non-zero 'arg:' field, and those of
tag `DW_TAG_auto_variable` always have a zero 'arg:' field.  These are
the only configurations that are properly understood by the backend.

(Also, fix the bad examples in LangRef and test/Assembler, and fix the
bug in Kaleidoscope Ch8.)

A large number of testcases seem to have bitrotted their way forward
from some ancient version of the debug info hierarchy that didn't have
`arg:` parameters.  If you have out-of-tree testcases that start failing
in the verifier and you don't care enough to get the `arg:` right, you
may have some luck just calling:

    sed -e 's/, arg: 0/, arg: 1/'

or some such, but I hand-updated the ones in tree.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243183 91177308-0d34-0410-b5e6-96231b3b80d8

docs/tutorial/LangImpl8.rst

@@ -397,7 +397,7 @@ argument allocas in ``PrototypeAST::CreateArgumentAllocas``.
                                       KSDbgInfo.TheCU.getDirectory());
   DILocalVariable D = DBuilder->createLocalVariable(
       dwarf::DW_TAG_arg_variable, Scope, Args[Idx], Unit, Line,
-      KSDbgInfo.getDoubleTy(), Idx);
+      KSDbgInfo.getDoubleTy(), true, 0, Idx + 1);
 
   Instruction *Call = DBuilder->insertDeclare(
       Alloca, D, DBuilder->createExpression(), Builder.GetInsertBlock());