core: Log a debug message when a module overrides a check

This can help locate checks gone astray when using modules that
can override them.

Signed-off-by: Andreas Ericsson <ae@op5.se>
Mark a bunch of deprecated/unimplemented external command macros

The following list got the chop and were replaced with
CMD_UNIMPLEMENTED_XX (where XX is the number they represent):
  CMD_CANCEL_HOST_DOWNTIME
  CMD_CANCEL_SVC_DOWNTIME
  CMD_CANCEL_ACTIVE_HOST_DOWNTIME
  CMD_CANCEL_PENDING_HOST_DOWNTIME
  CMD_CANCEL_ACTIVE_SVC_DOWNTIME
  CMD_CANCEL_PENDING_SVC_DOWNTIME
  CMD_CANCEL_ACTIVE_HOST_SVC_DOWNTIME
  CMD_CANCEL_PENDING_HOST_SVC_DOWNTIME
  CMD_FLUSH_PENDING_COMMANDS

Signed-off-by: Andreas Ericsson <ae@op5.se>
common/macros: Stop marking notes and *url as free-able service macros

They aren't, really, as we now assign by reference instead of
copying, and free()'ing them cause all sorts of weird behaviour
later.

Signed-off-by: Andreas Ericsson <ae@op5.se>
xodtemplate: Avoid free()'ing dependent hostlist multiple times

For the (rather unusual) case when we have hosts depending on
multiple others using hostdependencies, we used to crash with a
segfault when loading the configuration (regardless of whether we
verified it to start running or just as a part of a config restart
test thing).

The problem was due to some overexcited optimization on my behalf,
attempting to free() the variables of an inner loop while parsing
it, regardless of whether we needed to parse it again later or
not.

With this patch, the config verifies nicely and Nagios can load
it without problems.

Signed-off-by: Andreas Ericsson <ae@op5.se>