Added new type-safe cast functions.

This, when properly used, should get rid of most memory corruption issues,
currently, casting types C-style with no checks leads to some abstract crashing.
Functionality is same as with dynamic_cast<>, but with no RTTI check - so when
casting into invalid type you will receive NULL, and most probably crash.
At the same time, i took the liberty to convert most Player* casts to ToPlayer().
Still needs crapload of casts being moved to new facility.

--HG--
branch : trunk

src/game/DynamicObject.cpp

@@ -61,7 +61,7 @@ void DynamicObject::RemoveFromWorld()
             if(Unit *caster = GetCaster())
             {
                 if(caster->GetTypeId() == TYPEID_PLAYER)
-                    ((Player*)caster)->SetViewpoint(this, false);
+                    caster->ToPlayer()->SetViewpoint(this, false);
             }
             else
             {