[PATCH] Audit: Collect signal info when SIGUSR2 is sent to auditd

Makes the kernel audit subsystem collect information about the sending
process when that process sends SIGUSR2 to the userspace audit daemon.
SIGUSR2 is a new interesting signal to auditd telling auditd that it
should try to start logging to disk again and the error condition which
caused it to stop logging to disk (usually out of space) has been
rectified.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>