build-sys: move acl searching code into libsystemd-acl

This loop over acls is a bit too much to keep inside
of another loop.
journalctl: be smarter about journal error checks

There are many ways in which we can get those checks wrong, so it is
better to warn and then error out on a real access failure.

The error messages are wrapped to <80 lines, because their primary
use is to be displayed in the terminal, and it is easier to read them
this way. Reading them in the journal can be a bit trickier, but
this is a bug in logs-show.c.
util: workaround two gcc warnings

gcc does not know that errno cannot be negative, and warns
about unitialized variables later on. Kill the warnings by
returning -errno only after checking that errno is positive.
udev/collect: avoid initalizing memory twice