Fix pg_dumpall on pre-8.1 servers

rolname did not exist in pg_shadow.

Backpatch to 9.3

Report by Andrew Gierth via IRC
Always use the same way to addres a descriptor in ecpg's regression tests.
Add OVERLAPS to index in the docs.

Per report from Adam Mackler and Jonathan Katz
Fix calculation of ISMN check digit.

This has always been broken, so back-patch to all supported versions.

Fabien COELHO