coredump: honour RLIMIT_CORE when saving/processing coredumps With this change processing/saving of coredumps takes the RLIMIT_CORE resource limit of the crashing process into account, given the user control whether specific processes shall core dump or not, and how large to make the core dump. Note that this effectively disables core-dumping for now, as RLIMIT_CORE defaults to 0 (i.e. is disabled) for all system processes.

sysctl: use %P instead of %p in core pattern That way we'll get the PID on the host, rather than the one in a PID namespace. Which should make the coredump handler less confusing. Fixes #1930.

man: add systemd-coredump(8) and a bunch of links

sysctl: coredump.conf -> 50-coredump.conf