If `/boot/intel-ucode.img` is present, update-extlinux will add it as
(first) INITRD. This way the microcode update in package non-free/intel-ucode
will be automatically loaded, if installed. This package fixes, among other
processor bugs, the hyper-threading bug in Intel Skylake and Kaby Lake
processers currently in the news [1]. More details here [2] and here [3].

[1] https://lists.debian.org/debian-devel/2017/06/msg00308.html
[2] https://wiki.archlinux.org/index.php/Microcode#Syslinux
[3] https://wiki.gentoo.org/wiki/Intel_microcode

minor fix that makes it work with bash

on lxc we dont have the boot device available so extlinux will fail.
We cannot check for `openrc --sys` because apk run the trigger in chroot
and grsecurity will prevent openrc access /proc/1/environment.

So we simply add a --warn-only option and use that from trigger.

the vanilla kernel does not have any -* suffix so it needs special
handling.

fixes #2761

and trivial fix for comment in conf

We allow a password to be set in /etc/update-extlinux.conf. Instructions for
generating this are in /etc/update-extlinux.conf. For reference, here is another
(equivalent) way to generate the MD5 password: openssl passwd -1 -salt yy pass

If one sets a password, one will presumably want to make
/etc/update-extlinux.conf world-unreadable. We don't do that for you; however
we do make sure when a password is present to make the /boot/extlinux.conf
files we generate be world-unreadable.

Of the auto-generated entries, only HDT (if this is generated) is now
configured to respect the password; however, you can include "MENU PASSWD" in
any entries you put in /etc/update-extlinux.d/.

For example, I configure my BIOS to only boot from the internal drive, but I
have an entry in /etc/update-extlinux.d that permits chain-booting from a USB
key, and I have this entry configured to also require the password. (The BIOS
is also passworded, so that these settings can't be changed willy-nilly.)

Conflicts:
	main/syslinux/update-extlinux.conf