Added php-apc to Recommends: line in debian/control [#CC-4991]
CC-4997: don't exit install script with non-zero value if airtime-check-system fails

-fixed
Merge branch '2.3.x' of dev.sourcefabric.org:airtime into 2.3.x
Merge branch '2.3.x' into cc-4979-add-fourth-switch