Return a `minigen_t` struct with explicit width and height instead of extending the UINT8 buffer by 2 to provide that information in a very datatype-limited way.
Lines, sides, sectors, and things now all support the "Custom" tab properly. Label a property as `user_[whatever you want]` in this tab, and it will be added to the structure. ACS will then be able to retrieve it using the `Get[x]UserProperty()` function.
This caused some scary issues with P_SaveNetGame the other day, and it's making ACS net sync harder. Let's just cut this off right now.
Also fixed some scary mix-ups in some of the Lua archiving code.
