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/Parser/struct-recursion.c b/test/Parser/struct-recursion.c
new file mode 100644
index 0000000..c16f9fc
--- /dev/null
+++ b/test/Parser/struct-recursion.c
@@ -0,0 +1,11 @@
+// RUN: clang %s -fsyntax-only
+
+// C99 6.7.2.3p11
+
+// mutually recursive structs
+struct s1 { struct s2 *A; };
+struct s2 { struct s1 *B; };
+
+// both types are complete now.
+struct s1 a;
+struct s2 b;