* Create a FILTER_DECL() macro that initializes the 'struct filter' object,
   with all members properly initialized. Then -Wno-missing-field-initializers
   can be removed from CFLAGS.

 * Implement the knote_modify() hook for all filters.

 * Add a dbg_printf() statement within kevent_wait() to report the value
   of the timeout.

 * Refactor kevent_copyin() to remove the goto statements.

 * Fix the crasher w/ corruption in test/vnode.c

 * Add the kevent64() syscall as implemented on MacOS X. This guarantees
   that 64-bit values can be used in the 'udata' field on 32-bit platforms.

 * Check other filters for the EV_DISPATCH bug that was fixed in r252.