failsafe-mode: print short help on commandline

failsafe-mode: print short help on commandline

[base-files] failsafe-mode: print short help on commandline

Like mentioned in ticket https://dev.openwrt.org/ticket/11911
this should make the IRC much quieter. Failsafe is somehow
special and even experienced users are helpless, because they
are not used to this seldom situation. Also: likely you have
no internet access in this mode, so you cannot use the wiki.

a failsafe-session now looks like this:
first we see from 'package/base-files/files/bin/login.sh' the hint:

 === IMPORTANT ============================
  Use 'passwd' to set your login password
  this will disable telnet and enable SSH
 ------------------------------------------

after this the /etc/banner ("OpenWrt - wireless freedom")
and then the new text:

================= FAILSAFE MODE active ================
special commands:
* firstboot          reset settings to factory defaults
* mount_root     mount root-partition with config files

after mount_root:
* passwd                         change root's password
* /etc/config               directory with config files

for more help see:
http://wiki.openwrt.org/doc/howto/generic.failsafe
=======================================================

this supersedes the old patches:
http://patchwork.openwrt.org/patch/3337/
http://patchwork.openwrt.org/patch/3553/

Signed-off-by: Bastian Bittorf <bittorf@bluebottle.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42985 3c298f89-4303-0410-b956-a3cf2f4a3e73