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/CreateInvocationFromCommandLine.cpp b/lib/Frontend/CreateInvocationFromCommandLine.cpp
index 653da75..b477ade 100644
--- a/lib/Frontend/CreateInvocationFromCommandLine.cpp
+++ b/lib/Frontend/CreateInvocationFromCommandLine.cpp
@@ -30,7 +30,7 @@
 /// argument vector.
 CompilerInvocation *
 clang::createInvocationFromCommandLine(ArrayRef<const char *> ArgList,
-                            llvm::IntrusiveRefCntPtr<DiagnosticsEngine> Diags) {
+                            IntrusiveRefCntPtr<DiagnosticsEngine> Diags) {
   if (!Diags.getPtr()) {
     // No diagnostics engine was provided, so create our own diagnostics object
     // with the default options.