Petitboot v1.9.0 released

[Samuel Mendoza-Jonas]

Petitboot v1.9.0 has been tagged. A few notable fixes and additions include:

- OpenSSL support for signed boot
Encrypted/signed boot has been extended to support both GPGme and OpenSSL, see
the --with-signed-boot configure option.

- A number of fixes to parser code

- Periodic network requery & support for the 'reboottime' DHCP option.
Petitboot will now periodically requery network parameters; re-acquiring its
DHCP lease or re-downloading a statically defined URL if configured. The
frequency of this query can be controlled from the DHCP server via the
'reboottime' PXELINUX option, which defaults to five minutes.

- Non-boot-cancelling keys and temporary overrides
In a nod to other bootloaders the keys F10-F12 now apply temporary autoboot
settings (disk, USB, and network respectively). The Ctrl-L key combination also
no longer interrupts boot when refreshing the display.

- IPv6
Petitboot now supports IPv6, including changes to support IPv6 addresses and
URLs, and the udhcpc6 Busybox client. udhcpc6 supports stateful DHCPv6 and
handles the usual 'pxeconffile' and 'pxepathprefix' options. The DHCPv6 option
'bootfile_url' is also recognised by Petitboot.

- Jenkins pipeline jobs & Docker additions
Jenkins trigger and build jobs have been added and a few improvements to the
Docker scripts for those who like to continuously integrate.

- ARM64 & efivar support
A big series from Geoff and Ge Song that adds a platform-arm64 platform
definition, moves a lot of generic platform code into platform.c and
lib/param_list, as well as a host of cleanups and fixes. Note that these changes
may mean that a platform needs to be explicitly configured with
--enable-platform-foo depending on the build host, but most users should find
it configures the correct platform automatically.