terminal/subterm: use usec_t instead of "unsigned long"

Avoid hard-coding "unsigned long" and use the usec_t type defined in
src/shared.
barrier: convert msecs to usecs in test-code

Avoid using msecs in favor of usec_t. This is more consistent with the
other parts of systemd and avoids the confusion between msec and usec. We
always use usecs, end of story.
time-util: add and use USEC/NSEC_INFINIY
login: update systemd-user PAM configuration file
udevd: add --event-timeout commandline option

Some events take longer than the default 30 seconds. Killing those
events will leave the machine halfway configured.

Add a commandline option '--event-timeout' to handle these cases.
udev: unify event timeout handling
build-sys: remove systemd-coredumpctl symlink
udev: place opening { at the same line as the function declaration
factory: install minimal PAM and nsswitch config
test: test_tables - fix missing symbols when --gc-sections are not available
build-sys: add missing files for distcheck