Added back the code that set the offset of variables with the offsetof function. This
code is running by default. Any code that includes #ifndef TRICK_ICG in
classes/structures will want this on.
Added a flag to ICG that allows us to turn off writing of these lines. If the flag
is present, ICG may write out io_src code for private/protected variables that it could
not reach if an offsetof function was required. Code cannot have any #ifndef TRICK_ICG
present in classes/structures for this to work.