Re: PROPOSAL: Split uiomove into uiopeek, uioskip

[Taylor R Campbell <campbell+netbsd-tech-kern%mumble.net@localhost>]

If we think too hard about making this precise we'll wind up with
names like uiosimulateviolatingnocloningtheorem and uiowavecollapse.

uioskip serves either to discard data without consuming it, or to
advance the pointer after using the data with uiopeek.

peek is in contrast to get, like bufq_get/peek -- it's nondestructive
of the queue/transfer.  Probably won't be used much in the UIO_READ
direction (i.e., writing data into a user's buffer) but who knows.
None of these opposites are perfect: bufq_poke would be bonkers,
memcpy vs memmove is hopeless, and nothing here actually destroys the
source object like C++ move semantics vs copy semantics which more
accurately reflect the physical meanings of the English words.

I'm more interested in how the nuclear reactor is going to work!