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.

llvm-svn: 243183
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 17ee4b3..c503598 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -3906,12 +3906,12 @@
 
 .. code-block:: llvm
 
-    !0 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "this", arg: 0,
+    !0 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "this", arg: 1,
                           scope: !3, file: !2, line: 7, type: !3,
                           flags: DIFlagArtificial)
-    !1 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "x", arg: 1,
+    !1 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "x", arg: 2,
                           scope: !4, file: !2, line: 7, type: !3)
-    !1 = !DILocalVariable(tag: DW_TAG_auto_variable, name: "y",
+    !2 = !DILocalVariable(tag: DW_TAG_auto_variable, name: "y",
                           scope: !5, file: !2, line: 7, type: !3)
 
 DIExpression
diff --git a/llvm/docs/tutorial/LangImpl8.rst b/llvm/docs/tutorial/LangImpl8.rst
index 0b9b39c..88224bb 100644
--- a/llvm/docs/tutorial/LangImpl8.rst
+++ b/llvm/docs/tutorial/LangImpl8.rst
@@ -397,7 +397,7 @@
                                       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());