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

lib/IR/Verifier.cpp

@@ -1063,6 +1063,8 @@ void Verifier::visitDILocalVariable(const DILocalVariable &N) {
          "invalid tag", &N);
   Assert(N.getRawScope() && isa<DILocalScope>(N.getRawScope()),
          "local variable requires a valid scope", &N, N.getRawScope());
+  Assert(bool(N.getArg()) == (N.getTag() == dwarf::DW_TAG_arg_variable),
+         "local variable should have arg iff it's a DW_TAG_arg_variable", &N);
 }
 
 void Verifier::visitDIExpression(const DIExpression &N) {