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/examples/clang-interpreter/main.cpp b/examples/clang-interpreter/main.cpp
index ce5c5f9..c39468a 100644
--- a/examples/clang-interpreter/main.cpp
+++ b/examples/clang-interpreter/main.cpp
@@ -72,7 +72,7 @@
   TextDiagnosticPrinter *DiagClient =
     new TextDiagnosticPrinter(llvm::errs(), DiagnosticOptions());
 
-  llvm::IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
+  IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
   DiagnosticsEngine Diags(DiagID, DiagClient);
   Driver TheDriver(Path.str(), llvm::sys::getDefaultTargetTriple(),
                    "a.out", /*IsProduction=*/false, Diags);