libclang: use getCursorTU and getCursorASTUnit instead of explicit casts


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172241 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/libclang/CXCursor.cpp b/tools/libclang/CXCursor.cpp
index 9508962..8a9cf23 100644
--- a/tools/libclang/CXCursor.cpp
+++ b/tools/libclang/CXCursor.cpp
@@ -805,7 +805,7 @@
 }
 
 ASTUnit *cxcursor::getCursorASTUnit(CXCursor Cursor) {
-  CXTranslationUnit TU = static_cast<CXTranslationUnit>(Cursor.data[2]);
+  CXTranslationUnit TU = getCursorTU(Cursor);
   if (!TU)
     return 0;
   return static_cast<ASTUnit *>(TU->TUData);