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/lib/Frontend/ASTMerge.cpp b/lib/Frontend/ASTMerge.cpp
index d33e0ea..f3e6ea8 100644
--- a/lib/Frontend/ASTMerge.cpp
+++ b/lib/Frontend/ASTMerge.cpp
@@ -37,10 +37,10 @@
                                          CI.getASTContext().getLangOptions());
   CI.getDiagnostics().SetArgToStringFn(&FormatASTNodeDiagnosticArgument,
                                        &CI.getASTContext());
-  llvm::IntrusiveRefCntPtr<DiagnosticIDs>
+  IntrusiveRefCntPtr<DiagnosticIDs>
       DiagIDs(CI.getDiagnostics().getDiagnosticIDs());
   for (unsigned I = 0, N = ASTFiles.size(); I != N; ++I) {
-    llvm::IntrusiveRefCntPtr<DiagnosticsEngine>
+    IntrusiveRefCntPtr<DiagnosticsEngine>
         Diags(new DiagnosticsEngine(DiagIDs, CI.getDiagnostics().getClient(),
                              /*ShouldOwnClient=*/false));
     ASTUnit *Unit = ASTUnit::LoadFromASTFile(ASTFiles[I], Diags,