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: set code width to 120

style: consistently align pointer with name

Run astyle with align-pointer=name

Share linker.h between architectures

x86: Add BSS regions for BOOT and PHYS code

Uninitialized data structures in BOOT and PHYS code currently get
placed in sections that are allocated in the file of the final image.
Whilst these sections will get reclaimed during kernel boot, so no
runtime memory is being wasted, it results in kernel images that
are much larger to load and transport than necesary.

This change adds explicit BSS regions for both BOOT and PHYS code
and moves all appropriate data structures into them

SELFOUR-624: fix ia32 debug build

- separate putDebugChar and putConsoleChar
- this only has effect on x86 where 2 serial ports are initialised by
the kernel
- for arm, putConsoleChar just calls putDebugChar

SELFOUR-624: remove redundancy in io.[c|h]

And clean up a bit while we are there

x86: Add link explaining BDA

x86: read default serial configuration from BDA

BDA - BiosDataArea

Fixes #28

Further separate 'release' and 'verification' builds

Originally building the kernel was largely considered to be done in
one of two ways
1. Release build with no assertions, no debug symbols and no printing.
This was generally considered to be a 'verified' build
2. Debug build with assertions, debug symbols and printing

Since then various options were added, such as the 'code injection'
option, which we wanted on builds that did not have assertions or
other options that affected performance. As such it did not depend
upon a debug build and had large warning signs saying that enabling
this in a release build would not give you a verified or trusted
kernel.

Most recently the ability to print from the kernel in release mode
was added. For the same reason that tying the ability to print with
the performance reduction of various debugging was not always desireable.

This change attempts to unify the current state and have a single top
level option to enable a 'verification friendly' build. All other
options (assertions, printing, code injection) then depend upon
this configuration not being set.

x86: Rename ia32->x86

This is a stylistic commit to make names of variables/constants and
functions in the kernel more consistent. That is, things that are
not IA32 specific, but are generic x86, get renamed to having an
x86 name

x86: Do not conditionally compile IOMMU code, use build/run time checks

Guarding code with #ifdef's makes even cursor testing of 'does this code compile'
difficult due to code being hidden by the pre-processor. Using config_set in
regular C if statements is performant as the compiler can trivially detect
dead code at compile time, and at -O1 and above will not even link in symbols
referenced by dead code in these blocks, so this will not bloat image size

x86: Strip multi kernel support from the x86 kernel. This is not used and is conflicting with planned future features

Make utility functions 64bit friendly

Rationalize standard types

This commit aims to rationalize how we represent different types
for compatiblity between ARM and x86, as well as between 32 and
64 bit code. The choices being made here is to declare that a
uint32_t has a type of 'int', this allows uint32_t to be declared
consistently across 32 and 64 bit (at least in GCC).
The word_t type is declared using a 'long' (not a uint32_t or uint64_t) to
allow for a word_t to be backed by the same type on both 32 and 64 bit
All other types that want to be declared as the size of a native word
get declared in terms of a word_t

fix format strings for x86

xIntroduce RELEASE_PRINTF, which allows a renamed printf (release_printf) to be used in a release build of the kernel - userful for debugging tests that only fail on a release build of the kernel

x86: Make x86 the name of the architecture instead of IA32

IA32 is 32bit version of the x86 architecture. Whilst only IA32
is supported, much of the code is generic x86. Using a generic
x86 architecture will aid in future 64bit support