Mention the paragraphs in the standards which sanction TBAA.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@116617 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CodeGenTBAA.cpp

@@ -7,7 +7,11 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This is the code that manages TBAA information.
+// This is the code that manages TBAA information. Relevant standards
+// text includes:
+//
+//   C99 6.5p7
+//   C++ [basic.lval] (p10 in n3126, p15 in some earlier versions)
 //
 //===----------------------------------------------------------------------===//