I added that because I wanted to make it clear there was 4B we could use in the future (I always have to  figure that out again, every time I look at this structure).

I used an "int" because WT_PAGE_STATE is an enum which is an int, we're basically assuming an "int" is 4B in this structure layout.  I added a check against WT_REF_SIZE because I think we want to know if we run into a system with 8B enums or that is padding this structure in a new way.  I think it will all still work, but I'd want to think about it when it happens.

If you'd rather use uint32_t, that would be OK with me.