add kevent.o, kqueue.o, kqueue.2, kevent.2
pull in <sys/event.h>
document differences in netbsd implementation:
* we don't have rfork or AIO, so don't talk about it
* filter, flags and fflags are now uint32_t
* document KFILTER_BYFILTER and KFILTER_BYNAME ioctls
* expand filter description
add kfilter_register(9), knote(9)
add rudimentary support for displaying DTYPE_KQUEUE fds
* change various struct elements from short, u_short, int or u_int to uint32_t
* change data to uintptr_t
* change EVFILT* from -1..-6 -> 0..5
* add p_opaque element to struct knote.union kn_ptr
* add more comments, cleanup whitespace
* add struct kfilter_mapping, and ioctls which use it:
	KFILTER_BYNAME		map name -> filter
	KFILTER_BYFILTER	map filter -> name
  as well as two temporary debugging ioctls
	KFILTER_REGISTER	register name to given filter
	KFILTER_UNREGISTER	unregister name
* prototype kfilter_register(9) and kfilter_unregister(9)
* cleanup whitespace
* rename KQEXTENT -> KQ_EXTENT (mmm, consistency)
* add KFILTER_MAXNAME and KFILTER_EXTENT
add event.h
add d_kqfilter to cdevsw, and initialize as appropriate. provide helper
macros as necessary.
add DTYPE_KQUEUE
add fo_kqfilter to struct file
add extra items for kqueue's use:
	fd_knlist	list of attached fd knotes, indexed by fd
	fd_knlistsize	size of fd_knlist
	fd_knhash	has table for attached non-fd knotes
	fd_knhashsize	size of fd_knhash
add M_KEVENT (119)
add struct klist p_klist to struct proc
add struct klist si_klist to struct selinfo
add SB_KNOTE (kernel note attached), and prototype for soo_kqfilter()
prototype ttykqfilter()
add struct klist v_klist to struct vnode, and prototype vn_kqfilter()
add kern/kern_event.c
* update for differences between netbsd & freebsd WRT:
	- header files
	- struct locking
	- pool (& other memory) allocation
	- timeouts
* add kqueue_ioctl(), to support ioctl(2) operations on a kqueue fd.
* change the way that system filters are referenced to support name lookups
  and unimplemented (yet known about) filter types (such as EVFILT_AIO)
* add kfilter_register(9): register filter with given name to map to given
  filterops. filter must not exist
* add kfilter_unregister(9): unregister user filter
* add kfilter_byname(): lookup filter by name, which can be a system filter
  or a user-added filter
* add kfilter_byfilter(): lookup filter by filter number
* in kqueue_register(), use kfilter_byfilter() to determine filterops rather
  than using obscure ~ operation (which was now incorrect due to renumbering)
* cleanup whitespace, improve comments
* check return code of all copyouts()s
add soo_kqfilter method