The current top-level Makefile has a fundamental problem which
makes "make oldconfig vmlinux" impossible:

It includes .config, which is changed by "oldconfig". So after "oldconfig"
.config has changed and the .config the Makefile had read is obsolete.
make provides a mechanism to cope with this, it'll restart automatically 
if any of the files it included changed, if you let it know that you
changed it, just using a normal rule which has .config as its target.

However, once you tell make that "make oldconfig" changes .config, you
have another problem: oldconfig always uses .config to be remade, there's
no mechanism to tell if it's up to date. So makes notices that .config
has changed, restarts, makes oldconfig again, notices that .config has
changed, restarts, ... you get the picture.

The way to solve this is to do a proper two-stage approach: If you just
say "make oldconfig", there's no need for the Makefile to even read the
.config. If it does not, it won't restart and recurse infintely.
So we divide the Makefile into two sections: One for targets which don't
need the variables from .config, like *config, clean, mrproper and
one section which does the actual build, which needs to know the
CONFIG_ options.

If one of the "noconfig" targets is given, we handle those, without
reading .config. From there, we call make again, filtering out the already
handled targets, to do the main work.

The fact that this actually works correctly can be seen by trying
"make vmlinux oldconfig" which will execute things in the right
order - and this is not just nitpicking, it means that "-j" will
get this case right, too.

The $(CONFIGURATION) hack used to start "make config" automatically
can go away now, too. Since we don't know which of make *config the
user prefers, we'll just ask him call "make whatever-config" himself,
instead of forcing "make config" on him.