dmesg: fix usage() typo

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
docs: note ddate removal

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
prlimit: delete rem_prlim prototype

We can just move the function up before any of its callers.

Signed-off-by: Davidlohr Bueso <dave@gnu.org>