This commit is a solution for the following problem:
Our snapshotbuilder - I will send a mail around in the next days for more
informations - will do the following tasks to generate a build:
* make distclean
* make allmodconfig
* changes target platform and other stuff in generated .config
* make oldconfig
* make
make oldconfig needs userinteraction and the user needs only to press
ENTER a few times (remeber: we changed some config values in step 3).
As we want to run our builds without userinteraction, we need something.
Now this commit introduces a new make target: snapshotupdate
It is equal to oldconfig, but uses data from stdin. So we can call e.g.
printf "\n" | make snapshotupdate (no user interaction)
instead of make oldconfig (with user interaction).
If somebody is not happy with this solution, commit a _working_ replacement,
which has the same functionality.
