Updated the plain-c++ manual test.

tests/manual/plain-cplusplus/main.cpp

@@ -122,7 +122,7 @@ int runWithNewPreprocessor(int argc, char *argv[])
 void parse(const char *fileName, const char *source, unsigned size)
 {
     Control control;
-    TranslationUnit unit(&control, control.findOrInsertStringLiteral(fileName));
+    TranslationUnit unit(&control, control.stringLiteral(fileName));
     unit.setSource(source, size);
     unit.parse();