$KBUILD_BUILD_TIMESTAMP is used in two places:
1. By mkcompile_h, to generate both the utsname::version string
2. By gen_initramfs_list.sh, to set the timestamps for the built-in initramfs
As we want utsname::version to contain the package version and not an
RFC822 timestamp, the current value doesn't work for (2).
Change mkcompile_h to prefer $KBUILD_BUILD_VERSION_TIMESTAMP over
$KBUILD_BUILD_TIMESTAMP, and set both variables in debian/rules.real.
svn path=/dists/trunk/linux/; revision=22647