There is no particular reason to keep this on it's own in the root of
the tree. Move it into the rest of the fine developer manual and fixup
any links to it. The only tweak I've made is to fix the code-block
annotations to mention the language C.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Claudio Fontana <cfontana@suse.de>
Message-Id: <20210223095931.16908-1-alex.bennee@linaro.org>