Enable a buildroot-based petitboot bootloader

Hi all,

The following series allows us to build a petitboot-based bootloader using buildroot.

Petitboot is a kexec-based bootloader; by plumbing together a few linux utilities, we can implement a bootloader in userspace, using standard Linux drivers for hardware support. There's a bit of background of petitboot in my recent linux.conf.au talk:

http://mirror.linux.org.au/linux.conf.au/2014/Thursday/89-Petitboot_doing_interesting_things_in_your_bootloader_-_Jeremy_Kerr.mp4

And the project homepage:

https://www.kernel.org/pub/linux/kernel/people/geoff/petitboot/petitboot.html

My primary target here is powerpc machines (and this series adds a defconfig to do a powerpc petitboot build), but I've also been able to get most of petitboot working when built as an EFI stub on x86 machines (we still need some platform-specific bits in petitboot for proper configuration persistence).

While most of this series is fairly straightforward, there are a few items that might need a little more attention:

- At the moment, I'm using my local repo for petitboot sources; it may be better to wait until everything is merged upstream. Upstream is still active, and I don't think this should take long.

- We add wide-char support for ncurses; this seems to be working okay, but could do with a little review.

- I still need a couple of tweaks to the target system (/etc/locale and /etc/inittab). At the moment, I'm carrying a change that introduces an overlay for these two files, but that's not suitable for upstream use:

     http://git.ozlabs.org/?p=buildroot;a=commitdiff;h=582c47a4

Is there any way I can provide updates to these files? The changes aren't board-specific; they're due to petitboot expecting to own the default consoles for UIs. Or is there a better way to do this?

This series is also available in my git tree, at:

git://git.ozlabs.org/~jk/buildroot/

- in the petitboot branch. Note that that branch includes the overlay too, which isn't intended for upstream.

Also, I'd like to give a big thanks to the buildroot developers; being able to re-roll an entire system with one command has made petitboot development *significantly* easier. Also, thanks to Thomas for the nudge to send these changes upstream!

Please let me know if you have questions/comments/etc.

Changes since v2:

- petitboot: is now autoreconfable, so drop the custom autoconf tomfoolery

- powerpc-utils, kexec-lite: Update upstream versions

- petitboot: use updated UDEV configuration options

- resync with package/Config.in changes

- drop already-merged changes

Changes since v1, based on feedback:

- drobbear: we only want a config option to disable the server, instead of both client and server

- ncurses: use NCURSES_LIBS-y

- busybox: fix HOOK_DIR glob expansion

- powerpc-utils, kexec-lite, petitboot: update upstream versions

- petitboot: add dependencies

- all: unified headers, now using full git SHAs

- dtc: Added patch to update to 1.4.0

Cheers,

Jeremy

---
Jeremy Kerr (7):
package/busybox: Add facility for DHCP hooks package/dropbear: Add separate configuration option for dropbear server package/ncurses: Allow building wide char support package/powerpc-utils: Add powerpc hardware utilities package/kexec-lite: Add a package for the kexec-lite tools package/petitboot: Add petitboot, the userspace bootloader Add powerpc64 petitboot defconfig