Clean up the relayd headers with help of include-what-you-use and some manual review. Based on common practice, relayd.h now includes the necessary headers for itself. OK benno@

Replace the protocol directives for HTTP with a new generic filtering language. The grammar is inspired by pf and allows to write versatile last-matching filter rules in protocol sections starting with the "pass", "block" or "match" keywords. This work was started almost two years ago and replaces large parts of relayd(8)'s HTTP and filtering code. The initial version reimplements and extends HTTP filtering, but will be improved to support generic TCP and other protocols later. With some testing, feedback, and help from benno@ and andre@. OK benno@

hoststated gets renamed to relayd. easier to type, and actually says what the daemon does - it is a relayer that pays attention to the status of pools of hosts; not a status checkers that happens to do some relaying

allow to add labels to protocol actions, they will be printed in http error pages and can be used to refer to additional information. ok pyr@