Documentation for the Closure_properties module.
Merge pull request #57 from yallop/closure_properties-doc

Documentation for the Closure_properties module.
Split compute_union_padding function.
Move arg_type to Static.
Perform bufferspec building entirely in the seal function.
Simplify the sealing of unpassable struct types.
Merge pull request #58 from yallop/simplify-bufferspecs

Simplify bufferspec implementation