Implement expansion of object-like macros.

Implement expansion of object-like macros.

For this we add an "active" string_list_t to the parser. This makes
the current expansion_list_t in the parser obsolete, but we don't
remove that yet.

With this change we can now start passing some actual tests, so we
turn on real testing in the test suite again. I expect to implement
things more or less in the same order as before, so the test suite now
halts on first error.

With this change the first 8 tests in the suite pass, (object-like
macros with chaining and recursion).