Remove support for variables that have been deprecated for a while.

variables deprecation revision
WITHOUT_NLS 2013-12-13 r336337
WITH_/WITHOUT_ 2014-02-24 r345870
NOPORT(DOC|EXAMPLE)S 2014-04-19 r351587
WITH_BDB_VER 2016-05-02 r414444
OVERRIDE_LINUX_BASE_PORT 2016-09-05 r421387
WITH_OPENSSL_(BASE|PORT) 2016-06-16 r416965

While there, add an ERROR variable that works like DEV_ERROR, but for
user facing errors, and move NOPORTDOCS,
NOPORTEXAMPLES and WITHOUT_NLS to it.

Cleanup bsd.sanity.mk a bit.

Fix fallout.

PR: 224613
Submitted by: mat
Exp-run by: antoine
Sponsored by: Absolight
Differential Revision: https://reviews.freebsd.org/D13490