Add warning about missing keyboard support.

linux.install

@@ -22,6 +22,12 @@ post_upgrade() {
   depmod ${KERNEL_VERSION}
   echo ">>> Generating initial ramdisk, using mkinitcpio.  Please wait..."
   mkinitcpio -p linux${KERNEL_NAME}
+
+  if [ $(vercmp $2 3.13) -lt 0 ]; then
+    echo ">>> WARNING: AT keyboard support is no longer built into the kernel."
+    echo ">>>          In order to use your keyboard during early init, you MUST"
+    echo ">>>          include the 'keyboard' hook in your mkinitcpio.conf."
+  fi
 }
 
 post_remove() {