libclang: introduce cxstring::{createRef,createDup} for StringRefs

Also migrate all clients from the old API.

llvm-svn: 174263
diff --git a/clang/tools/libclang/CIndexCodeCompletion.cpp b/clang/tools/libclang/CIndexCodeCompletion.cpp
index e287eda..61c5682 100644
--- a/clang/tools/libclang/CIndexCodeCompletion.cpp
+++ b/clang/tools/libclang/CIndexCodeCompletion.cpp
@@ -224,7 +224,7 @@
   if (!CCStr)
     return cxstring::createNull();
   
-  return createCXString(CCStr->getParentContextName(), /*DupString=*/false);
+  return cxstring::createRef(CCStr->getParentContextName());
 }
 
 CXString
@@ -923,7 +923,7 @@
   if (!Results)
     return cxstring::createEmpty();
   
-  return createCXString(Results->Selector);
+  return cxstring::createDup(Results->Selector);
 }
   
 } // end extern "C"