(Note that we only do this for the journal metadata, not for the xattrs,
as the xattrs are only supposed to store the original 1:1 info we
acquired from the kernel.)

strsignal() sucks, as it tries to generate human readable strings from
something that isn't really human readable by concept. Let's use
signal_to_string() instead, making this more grokkable. Difference is:
SIGINT gets translated → "SIGINT" rather than → "Interrupted".

…off trailing zeroes

Our coredump handler operates on a "context" supplied by the kernel via
the core_pattern arguments. When we pass off a coredump for processing
to coredumpd we pass along enough information for this context to be
reconstructed. This information is passed in the usual journal fields,
and that means we extended the 1s granularity timestamp to 1µs
granularity by appending 6 zeroes. We need to chop them off again when
reconstructing the original kernel context.

Fixes: systemd#4779

…edump file

We didn't include the resource limit field, add it.