serialized diagnostics: implement full deserialization of clang diagnostics via the libclang API.

I've tested it on simple cases and it works.  Test cases to follow as well as a few tweaks.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@144269 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/libclang/CXTranslationUnit.h b/tools/libclang/CXTranslationUnit.h
index 47d7146..b2b1b84 100644
--- a/tools/libclang/CXTranslationUnit.h
+++ b/tools/libclang/CXTranslationUnit.h
@@ -18,6 +18,7 @@
 struct CXTranslationUnitImpl {
   void *TUData;
   void *StringPool;
+  void *Diagnostics;
 };
 }
 
@@ -27,7 +28,7 @@
 namespace cxtu {
 
 CXTranslationUnitImpl *MakeCXTranslationUnit(ASTUnit *TU);
-
+  
 class CXTUOwner {
   CXTranslationUnitImpl *TU;