Revert "Fetch Linux image and headers from unstable, no matter what version."

This reverts commit 76ebad46.

Squeeze's APT does not support globs for package names :/

config/chroot_apt/preferences

@@ -118,15 +118,39 @@ Package: linux-base
 Pin: release o=Debian,a=unstable
 Pin-Priority: 999
 
-Package: linux-headers-*
+Package: linux-headers-486
 Pin: release o=Debian,a=unstable
 Pin-Priority: 999
 
-Package: linux-image-*
+Package: linux-headers-2.6-common
 Pin: release o=Debian,a=unstable
 Pin-Priority: 999
 
-Package: linux-kbuild-*
+Package: linux-headers-2.6-486
+Pin: release o=Debian,a=unstable
+Pin-Priority: 999
+
+Package: linux-headers-3.0.0-2-common
+Pin: release o=Debian,a=unstable
+Pin-Priority: 999
+
+Package: linux-headers-3.0.0-2-486
+Pin: release o=Debian,a=unstable
+Pin-Priority: 999
+
+Package: linux-image-486
+Pin: release o=Debian,a=unstable
+Pin-Priority: 999
+
+Package: linux-image-2.6-486
+Pin: release o=Debian,a=unstable
+Pin-Priority: 999
+
+Package: linux-image-3.0.0-2-486
+Pin: release o=Debian,a=unstable
+Pin-Priority: 999
+
+Package: linux-kbuild-3.0.0
 Pin: release o=Debian,a=unstable
 Pin-Priority: 999