Basic: import IntrusiveRefCntPtr<> into clang namespace

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

llvm-svn: 150958
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index d418896..862a654 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -38,7 +38,7 @@
   : LangOpts(new LangOptions()) {}
 
 CompilerInvocationBase::CompilerInvocationBase(const CompilerInvocationBase &X)
-  : llvm::RefCountedBase<CompilerInvocation>(),
+  : RefCountedBase<CompilerInvocation>(),
     LangOpts(new LangOptions(*X.getLangOpts())) {}
 
 //===----------------------------------------------------------------------===//