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

Use explicit struct packing instead of using compiler asserts
to check that packing happened as expected

The ACPI standard says these fields are 32bits, not the size
of a machine word or pointer

Using an unsigned long instead of forcing to 32bits allows this code
to be reused in a 64-bit context

This is a paranoia commit as most compilers will not
pad members of a struct if they are all the same size,
but this commit ensures it.

The multiboot specification states that these fields are 32bits in sized,
not the size of machine pointer or integer.

It's become obsolete after correspongin Isabelle C parser change.