Basic: import IntrusiveRefCntPtr<> into clang namespace

The class name is long enough without the llvm:: added.
Also bring in RefCountedBase and RefCountedBaseVPTR.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150958 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/unittests/Basic/SourceManagerTest.cpp b/unittests/Basic/SourceManagerTest.cpp
index 14f5b22..65d57b6 100644
--- a/unittests/Basic/SourceManagerTest.cpp
+++ b/unittests/Basic/SourceManagerTest.cpp
@@ -40,12 +40,12 @@
 
   FileSystemOptions FileMgrOpts;
   FileManager FileMgr;
-  llvm::IntrusiveRefCntPtr<DiagnosticIDs> DiagID;
+  IntrusiveRefCntPtr<DiagnosticIDs> DiagID;
   DiagnosticsEngine Diags;
   SourceManager SourceMgr;
   LangOptions LangOpts;
   TargetOptions TargetOpts;
-  llvm::IntrusiveRefCntPtr<TargetInfo> Target;
+  IntrusiveRefCntPtr<TargetInfo> Target;
 };
 
 class VoidModuleLoader : public ModuleLoader {