Making the ignored return explicit

Trying to appease Coverity ;)
Fixing more unchecked returns

Ignored a return in Math::Abs(), fixed unchecked return for flags in
Npc::TurnToward().

Two others in the packet object: SetUnicodeString() and
SetUnicodeStringFlipped(), neither was checking if the conversion from
array to UC was working.
More unchecked returns in npcmod and utilmod