Fix a couple of bugs, add some new cool stuff.

1. Fix a todo in Parser::ParseTag, to recover better.  On code like
   that in test/Sema/decl-invalid.c it causes us to return a single
   error instead of multiple.
2. Fix an error in Sema::ParseDeclarator, where it would crash if the
   declarator didn't have an identifier.  Instead, diagnose the problem.
3. Start adding infrastructure to track the range of locations covered
   by a declspec or declarator.  This is mostly implemented for declspec,
   but could be improved, it is missing for declarator.

Thanks to Neil for pointing out this crash.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@40482 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Sema/arg-duplicate.c b/test/Sema/arg-duplicate.c
new file mode 100644
index 0000000..5d44a72
--- /dev/null
+++ b/test/Sema/arg-duplicate.c
@@ -0,0 +1,15 @@
+// RUN: clang -parse-ast-check %s
+
+typedef int x; 
+int f3(y, x, 
+       x)          // expected-error {{redefinition of parameter}}
+  int y, x, 
+      x;           // expected-error {{redefinition of parameter}}
+{
+  return x + y; 
+} 
+
+void f4(void) { 
+  f3 (1, 1, 2, 3, 4);   // expected-error {{too many arguments to function}}
+}
+