- Moved most of the guts of Makefile to Makefile.inc1 to become the
backend for the build system.
- The new Makefile doesn't suffer from problems including the wrong
sys.mk because it doesn't use anything in there or bsd.own.mk. So,
from now on, the proper build command is just `make world' (or
buildworld).
- The intermediate makefiles called Makefile.inc0 and Makefile.upgrade
fiddle with the OBJFORMAT and MAKEOBJDIRPREFIX variables so that
both aout and elf object trees can coexist. Makefile.upgrade contains
the aout->elf transition build.
- A cross build environment is now very close to reality. Specifying
TOOLDIR, setting OBJFORMAT and MAKEOBJDIRPREFIX allow that.
See the comments in Makefile for more info.
