replacing all ifndef with pargma once

All the kernel header files now use pargma once rather than the ifndef,
as the pre-processed C files do not change while header files
are protected with pargma once. This will also solve any naming issues
caused by ifndef.

Convert license tags to SPDX identifiers

This commit also converts our own copyright headers to directly use
SPDX, but leaves all other copyright header intact, only adding the
SPDX ident. As far as possible this commit also merges multiple
Data61 copyright statements/headers into one for consistency.

style: consistently align pointer with name

Run astyle with align-pointer=name

SELFOUR-444: Preemptible zeroing for retype.

Change to the order of operations and timing behaviour of
invokeUntyped_Retype. The Retype operation now zeroes the
entire range of the Untyped cap (if it is being used for
the first time) before installing any objects. This avoids
the need for long-running initialisation of large objects,
whose initial contents are always zero. The initial zeroing
phase is preemptible, and may take multiple timeslices to
complete.

Defined untyped size ranges in libsel4

SELFOUR-421 Introduce explicit device frames and untypeds

Kernel objects cannot be created from device untypeds, with the
exception of frames, which do not get zeroed and cannot be used
as an IPC buffer. Device untypeds additionally cannot be used
in the construction of ASID pools.

This then changes the API to the rootserver (i.e. bootinfo) to
send device untypeds instead of device frames. On ARM these
device untypeds are the same as the previously exported device
frame regions. On x86 PCI scanning is removed and all physical
memory addresses (that are not important for kernel integrity)
are released to the user.

In order to have bits in the frame and untyped caps on ARM the
number of software ASIDs had to be reduced from 2^18 to 2^17,
and the maximum untyped size reduced from 2^31 to 2^30

SELFOUR-114: remove duplication of seL4_MessageInfo_t, adjust naming to avoid cparser mangling

unsigned int -> word_t

Release snapshot