Mainly misc cleanups (and a fix for the C++ build), but there are a few important changes in here.
VM_OnEvent() has become VM_OnEvent(), VM_OnEventWithReturn(), VM_OnEventWithDist(), and VM_OnEventWithBoth() (the latter of which is only ever used once...). Of course, this required every call to VM_OnEvent() be changed.
memberlabel_t and vmstate_t have been changed to use the regular "int" type versus explicitly specifying int32_t as they did previously. The rationale for this change is simply that it looks cleaner, and I think we should move toward just using "int" in most cases where there's no particular reason to specify an explicit data type.
Also changes CON_KILLIT to just "return" instead of "continue". DONT_BUILD.