Better honor the following MK_ flags in etc/Makefile and etc/rc.d/Makefile:
- MK_AMD
- MK_ATM
- MK_AUDIT
- MK_BOOT
- MK_GSSAPI
- MK_JAIL
- MK_LPR
- MK_SENDMAIL
- MK_VI
- MK_WIRELESS
- MK_ZFS
Honor MK_GSSAPI and MK_PKGBOOTSTRAP a bit better in etc/Makefile
Add MK_NTP block to etc/rc.d/Makefile