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.

arm,SMP: Refactor irq_t structure for smp

Explicitly create a struct definition for irq_t on SMP Arm
configurations. This makes it a lot harder to mistakenly use the wrong
irq encoding when moving an irq between a cnode index and hardware irq
number / core. A couple areas where this was being handled incorrectly
was fixed as part of the refactor. When performing an ipi for masking
PPI interrupts, the idx encoding is used as it fits into a single word.

[SMP] Abstracted IRQ indexing to handle PPIs

irq_t is now a "virtual" interrupt type that encapsulates the
information of the core in case of a private interrupt. There is a
couple of macros that need to be defined on the interrupt controller
level to translate between virtual and hardware IRQs.

x86: IOAPIC/MSI syscalls

Restructure the x86 interrupt handling to allow for a more flexible
method of using IOAPIC and MSI interrupts. The essence of this change
is to allow for the user to pick, for both IOAPIC and MSIs, which
CPU vector to use. Additionally there is future support, in the API,
for seL4 to eventually protect MSI interrupts with the vt-d interrupt
routing tables.

API behaviour for legacy systems using the PIC is preserved

Part of SELFOUR-281

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

unsigned int -> word_t

ioapic: refactored C code and first attempt at haskell spec

Support IOAPIC on ia32 and modify interrupt handling to support user level setting of modes

Release snapshot