ktr/ktrdump bugs

* The manpage says:

   Event Masking
     Event levels can be enabled or disabled to trim excessive and overly ver-
     bose logging.  First, a mask of events is specified at compile time via
     the KTR_COMPILE option to limit which events are actually compiled into
     the kernel.  The default value for this option is for all events to be
     enabled.

But this appears not to be true.  I have to set KTR_COMPILE=KTR_ALL in
the kernel config in order to get anything at all out of ktr
(i.e. even setting KTR_MASK=KTR_ALL doesn't register any events).

* ktrdump -i is undocumented in the manpage (but is listed in usage)

* ktrdump -i doesn't appear to work:

dosirak# sysctl debug.ktr
debug.ktr.cpumask: -1
debug.ktr.mask: 8388608
debug.ktr.entries: 1024
debug.ktr.version: 1
debug.ktr.verbose: 0
debug.ktr.alq_max: 0
debug.ktr.alq_cnt: 3596
debug.ktr.alq_failed: 0
debug.ktr.alq_depth: 1024
debug.ktr.alq_file: /c/ktr.out
debug.ktr.alq_enable: 1

dosirak# ktrdump -i /c/ktr.out
index  trace
------ -----
Segmentation fault (core dumped)

Kris