- add sysupgrade support for combined images by providing a platform.sh backend
- use the mtd fis partition table rewrite facility to resize partitions on demand
- generate generic combined images for the atheros target
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@17668 3c298f89-4303-0410-b956-a3cf2f4a3e73
