use from_i32 rather than from_uint and casting
tell emacs flycheck where to find the crate root
revise query/update/execute API; add bind()
 - next() becomes step()

add exec()

open database files using explicit authority
 - factor connect() out of new()
 - export mod ffi, core, access from crate root

--HG--
extra : amend_source : 1321d5c37ef36671347cf87fdceece40392ed515
update example in crate doc