Move mail.rc install to usr.bin/mail.

This leverages CONFS to do the install

Approved by:	re (blanket, pkgbase), bapt (mentor)
Differential Revision:	https://reviews.freebsd.org/D17216

etc/Makefile

@@ -34,10 +34,6 @@ BIN1+=	${SRCTOP}/usr.bin/locate/locate/locate.rc
 BIN1+=	hosts.lpd printcap
 .endif
 
-.if ${MK_MAIL} != "no"
-BIN1+=	${SRCTOP}/usr.bin/mail/misc/mail.rc
-.endif
-
 .if ${MK_OPENSSL} != "no"
 SSL=	${SRCTOP}/crypto/openssl/apps/openssl.cnf
 .endif

usr.bin/mail/Makefile

@@ -1,6 +1,7 @@
 #	@(#)Makefile	8.2 (Berkeley) 1/25/94
 # $FreeBSD$
 
+CONFS=	misc/mail.rc
 PROG=	mail
 SRCS=	version.c cmd1.c cmd2.c cmd3.c cmdtab.c collect.c edit.c fio.c \
 	getname.c head.c v7.local.c lex.c list.c main.c names.c popen.c \