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/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index d418896..862a654 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/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())) {}
 
 //===----------------------------------------------------------------------===//