Drop __DECONST as well as few fixes of style(9).

Phabric:	D1012
Suggested by:	mjg, jhb
Reviewed by:	mjg, jhb
Sponsored by:	QNAP Systems Inc.


git-svn-id: svn+ssh://svn.freebsd.org/base/head@273761 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f