. split user-editable and system-owned files in etc/Makefile
. mtab is a symlink, not a file now; remove it
. force-install of certain system-controlled /etc files from
top Makefile
. rename /etc/make.conf to /etc/mk.conf; and don't set $ARCH;
reduce difference in bsd.own.mk
Change-Id: I9f4bbb8d37ba80cba7dcfcf1a9a89e934910f579
