Fix tests.

As we use the main library of gtest (if already installed)
we don't need to (and must not) define a main function for the tests.

Does the same (use main library) if we use the subproject.

test/stringTools.cpp

@@ -54,8 +54,3 @@ TEST(stringTools, split)
 }
 
 };
-int main(int argc, char** argv)
-{
-  ::testing::InitGoogleTest(&argc, argv);
-  return RUN_ALL_TESTS();
-}