Enhanced process coredump routines.

This brings in the following features:

1. Limit number of cores per process via the %I coredump formatter.

Example:

if corefilename is set to %N.%I.core AND num_cores = 3, then
if a process "rpd" cores, then the corefile will be named
"rpd.0.core", however if it cores again, then the kernel will
generate "rpd.1.core" until we hit the limit of "num_cores".

this is useful to get several corefiles, but also prevent filling
the machine with corefiles.

2. Encode machine hostname in core dump name via %H.

3. Compress coredumps, useful for embedded platforms with limited space. A sysctl kern.compress_user_cores is made available if turned on.
   
   To enable compressed coredumps, the following config options need to be set: options COMPRESS_USER_CORES device zlib # brings in the zlib requirements. device gzio # brings in the kernel vnode gzip output module.

4. Eventhandlers are fired to indicate coredumps in progress.

5. The imgact sv_coredump routine has grown a flag to pass in more

state, currently this is used only for passing a flag down to compress
the coredump or not.

Note that the gzio facility can be used for generic output of gzip'd
streams via vnodes.

Obtained from: Juniper Networks