Add new library function set_ok,... and mp_exit

This should help with plugins which accumulate state and output
durign different states of the check.
Add a first rabbitmq check
User sharness to unittest checks
Detect missing slaves
Move some common options to curl_utils.
Port parameters from check_rabbitmq
Use new curl_utils functions.
Update check unit test
oops, a line was lost
Improve help/man for rabbitmq/buildbot checks.
Let git ignore sharnes output
Fix new json-c api
Merge branch 'rabbitmq'

Conflicts:
	curl/check_buildbot_slave.c