efi-boot-generator: simplify
machinectl: use initialization instead of zeroing
bus: export libsystemd-bus as a public library

Old static libsystemd-bus.la becomes libsystemd-bus-internal.la.
memfd functions are also exported in the same library.

(Best viewed with --color-words -U0).
bus: add public libsystemd-event
systemd_pam: treat debug as debug=1 and parse all params

systemd_pam would ignore all params after the first invalid one.
Instead ignore just this one, and parse the rest. There's just
one now, but as a matter of principle ;)

Also, allow debug as an alias for debug=1, and don't treat
invalid debug= options as fatal.
pam_systemd: port to libsystemd-bus