libclang: constness for CXString

llvm-svn: 172270
diff --git a/clang/include/clang-c/CXString.h b/clang/include/clang-c/CXString.h
index 74c3166..34cab5e 100644
--- a/clang/include/clang-c/CXString.h
+++ b/clang/include/clang-c/CXString.h
@@ -36,7 +36,7 @@
  * with the string data, call \c clang_disposeString() to free the string.
  */
 typedef struct {
-  void *data;
+  const void *data;
   unsigned private_flags;
 } CXString;