with make TESTS='test_1 test_2 ...' regress now it's possible to run only that specified subset of tests. It's really useful during debugging :)

The tests are still there, the suite is equivalent to the old one, but this one is better structured. The biggest annoyance I had with the old one was that it wasn't straightforward to test only a specific set of tests. It's still impossible, but it's way easier to do it now. This extract all the tests to their own functions. It's overall better in all possible regards.

`printf | openssl` is ugly :/

and while there reorder the targets in the Makefile a bit

the 1024 bytes limits is for the META only, not for the whole response. That means that the maximum size for the header line is 1029!

this unlocks the full regress tests on arch, for instance, or every OS where we don't have strl*