Remove some unused #defines.

Does not affect verification.
libsel4: Unify ARM/IA32 IPC buffer functions.

Implements two trivial functions that were present for IA32, but not included
in the corresponding ARM header.

Closes SELFOUR-226
trivial: Remove unimplemented function prototype.
trivial: Print domain values as unsigned integers in user errors.

With the comparison preceding this being done on unsigned integers, this avoids
confusing error messages like '-2147482648 >= 1'.
trivial: Standardise on 32-bit unsigned variables for domain values.

Domains are unnecessarily treated explicitly as 8-bit values within boot info.
Though there are existing proof constraints that limit the maximum domain value
to 8 bits, most of the code would permit domain values up to 32 bits. The
maximum value is unnecessarily constrained in boot info, a restriction which
this commit removes.

Closes VER-341
Merge branch mfernandez-master into master
Merge branch mfernandez-unused-defines into master
Merge pull request #38 from mfernandez/trivial

trivial: Print domain values as unsigned integers in user errors.
bf gen: Fix whitespace in constructors and getters.
bf gen: Fix missing include.

The bitfield generator uses the macros CONST and PURE which, for libsel4, are
defined in macros.h.