Implement (unreliable) button detection using code from ipodlinux bootloader - this needs replacing by a better button driver in firmware/ and triple-boot bootloader functionality. Current button mappings: MENU loads rockbox.ipod and checks the checksum (but doesn't execute it), PLAY will load and execute a Linux kernel (linux.bin). An error in either of those two actions, or no keypress will load the original firmware
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@7848 a1c6a512-1295-4272-9138-f99709370657