Build and run tests in one target

It's really only a minor thing, but I would really like to build and run tests in on command.

Currently, make test will only run the tests nothing else. Sadly, it's not possible to define dependencies on built in target.

So we would need to introduce a new target for that ('check', 'checks' or 'tests' is quite common).

Second, if we do that, what do you think about removing tests from target 'all'? So all simple make would build the library and make tests would build and run the tests.