Clean up the ldb python bindings to be 64 bit safe.

Clean up the ldb python bindings to be 64 bit safe.

Thanks in particular to arkanes and KirkMcDonald on #python for their
assistance, suggesting breaking the DN check.

I eventually found it while trying to cut down on the number of gcc
warnings, which is why we also add printf annotations.

Andrew Bartlett
(This used to be commit ba30e82d4efcba23c49622de43d3d6fc9c800e35)