Patch merged into filo/master: 00e82ca makefile: recreate version.h only when needed

the following patch was just integrated into master:
commit 00e82ca97042907951ee977ead2e93039ab1da6d
Author: Mathias Krause 
Date:   Tue Mar 6 13:26:48 2012 +0100

makefile: recreate version.h only when needed

Don't recreate version.h on each make invokation but only when needed, i.e.
    when the make variables have changed. Also make version.h a prerequisite for
    the object files to rebuild them when the version information changes.

Change-Id: I27a057be25902233ac0751db8061e9ad4cd50642
    Signed-off-by: Mathias Krause

Build-Tested: build bot (Jenkins) at Wed Mar  7 16:46:48 2012, giving +1
Reviewed-By: Stefan Reinauer  at Wed Mar  7 17:44:44 2012, giving +2
See http://review.coreboot.org/745 for details.

-gerrit