Realistic Roofs.

[Vas]

What I don't like about the current roofs, is that a single block anywhere within 7 blocks of the roof, can hold it up, even if the roof isn't even attached.  I've come up with a set of rules each roof tile must follow.  This should help preserve some realistic roof cliff type areas and such, and allow buildings to do more things.  I'll have to explain better when I get home though if necessary.

A roof must have 4+ walls supporting it within 9 blocks range, in order to not collapse.
A roof must have 3 walls supporting it within 7 blocks range, in order to not collapse.
A roof must have 2 walls supporting it within 5 blocks range, in order to not collapse.
A roof must have 1 walls supporting it within 3 blocks range, in order to not collapse.