Move land check functions to the top

[emmiegit]

Minor PR that is a complement to #212.

It standardizes the function such that land check functions appear at the top rather than scattered throughout.

[jruderman]

Could these symmetric checks (crossroads/elemental) be moved from incompatible1() to incompatible()?

[emmiegit]

I see, incompatible() is the wrapper. You're suggesting moving it because the symmetry means additional checks are being performed that are not necessary.