Move cron.d/at to usr.bin/at/

This helps with pkgbase as it tags this as a config file so it is handled as
such

Approved by:	allanjude (mentor)
Sponsored by:	Essen Hackathon
Differential Revision:	https://reviews.freebsd.org/D16673

etc/Makefile

@@ -174,7 +174,6 @@ distribution:
 .if ${MK_BLUETOOTH} != "no"
 	${_+_}cd ${.CURDIR}/bluetooth; ${MAKE} install
 .endif
-	${_+_}cd ${.CURDIR}/cron.d; ${MAKE} install
 	${_+_}cd ${.CURDIR}/defaults; ${MAKE} install
 	${_+_}cd ${.CURDIR}/devd; ${MAKE} install
 	${_+_}cd ${.CURDIR}/gss; ${MAKE} install

etc/cron.d/Makefile

@@ -1,11 +0,0 @@
-# $FreeBSD$
-
-.include <src.opts.mk>
-
-.if ${MK_AT} != "no"
-FILES+=		at
-.endif
-
-BINDIR=		/etc/cron.d
-
-.include <bsd.prog.mk>

usr.bin/at/Makefile

@@ -2,6 +2,9 @@
 
 .include "${.CURDIR}/Makefile.inc"
 
+CONFS=	atrun
+CONFSDIR=	/etc/cron.d
+CONFSNAME=	at
 PROG=	at
 SRCS=	at.c panic.c parsetime.c perm.c
 LINKS=	${BINDIR}/at ${BINDIR}/atq \