iphone-6: new device APKBUILD

This is an APKBUILD for the iPhone 6 (WIP).

The iPhone 6 can do USB networking, although I haven't been able to achieve a graphical environment. It is flashed using konradybcio's pongoOS scripts (netboot ramdisk) and then the rootfs (environment: none or a "failed to mount root partition" message arises) is flashed via netboot. linux-headers is required to be installed as the build requires asm/types.h. make ARCH=arm64 mrproper is also required for the build to finish, otherwise it complains of an unclean directory.