[MEDIUM] add support for health-checks on other addresses

[MEDIUM] add support for health-checks on other addresses

Patch from Fabrice Dulaunoy. Explanation below, and script
merged in examples/.

This patch allow to put a different address in the check part for each
server (and not only a specific port)

I need this feature because I've a complex settings where, when a specific
farm goes down, I need to switch a set of other farm either if these other
farm behave perfectly well.

For that purpose, I've made a small PERL daemon with some REGEX or PORT
test which allow me to test a bunch of thing.