fix licenses

libutils: Rephrase FORCE_READ into something safer.

This commit rephrases the `FORCE_READ` macro to avoid an unorthodox use of
`volatile`. The change makes the read less malleable from the compiler's point
of view.

It also has the unintended side effect of slightly optimising this operation. On
x86, an optimising compiler now generates a single load, rather than a load
followed by a store to the (unused) local variable. On ARM, there is a similar
improvement, but we also save two instructions for stack pointer manipulation
depending on the context in which the macro is expanded.

Remove an unnecessary #include.

libutils: trivial: Replace ifdef guards with pragma once.

libutils: Added force.h

This file contains macros for forcing behaviour often optimized away by
compilers. For example, the FORCE_READ macro forces a read from a given
address, even if the read value is never used.