The patch allows userspace to issue printk's, via sys_syslog().

The main use of this is within hpa's klibc - initial userspace needs a
way of logging information and this API allows that information to be
captured into the printk ringbuffer.  It ends up in /var/log/messages.

Messages are truncated at 1024 characters by printk's vsprintf().

Requires CAP_SYS_ADMIN.