tmpfs_downsize(): store new size in v0

This is required by the squashfs_container module.
fix scripts/fs/pack/recipes/ro_rootfs_system.sh

don't exclude _all_ scripts in rootfs
scripts/initramfs/telinit: don't depend on busybox

Search in /bin, /sbin for swapoff/umount/...
lib/initramfs/misc: don't pass -c CON to switch_root
lib/initramfs/disk: don't die if fsck fails

TODO: examine fsck's return code
initramfs, newroot/tmpdir: fix symlink creation
initramfs vars: set LOGFILE
lib/net_setup: basic network configuration
initramfs: net_setup()
lib/initramfs: nfsmount

wrapper functions for mounting nfs filesystems
initramfs/core: expose nfsmount, net_setup functions
initramfs/default: bring down networking
initramfs, liram: accept nfs mounts as LIRAM_DISK

This allows to boot liram systems over pxe+nfs (no local disk involved).