GitLab

See https://kiwiirc.com/docs/webirc

fix #3135

make coverage will display an error instead

make coverage runs the test_suite and generates a report

`make check` is also added to compile and run the tests
Catch is fetched with cmake automatically into the build directory when needed

Both for me, and apparently for clang static analyzer, who reported a (imo)
false positive.

Introduce a script, which is called with different parameters, to have a
number of builds done with a different configuration, without repeating
things too much.