Get rid of magnum CI testing code
Tweak Jenkins CI settings
Clean libev and libeio by directly removing files instead of running 'make maintainer-clean'

This way, cleaning always works even when you've moved the Phusion Passenger directory.
Some Jenkins CI fixes

[ci:skip]
More Jenkins CI fixes

[ci:skip]
More Jenkins CI fixes

[ci:skip]
More Jenkins CI fixes

[ci:skip]
More Jenkins CI fixes

[ci:skip]
More Jenkins CI fixes

[ci:skip]