change apache::module from a class to a define, (it was changed in the apache module)
have passenger_stats munin script take an environment variable for the location of passenger-status
add a variable $passenger_bin_path to the passenger class
variable PASSENGER_STATUS does not need to be quoted with backticks.
Revert "variable PASSENGER_STATUS does not need to be quoted with backticks."

in fact it does need to be quoted with backticks since it needs to be run!

This reverts commit 6d6960713315ea52b12ca1d4cf696c3fb7c816fa.
Include apache to ensure subclass declarations work correctly.