Issue template created from web interface

Many tests were doing it manually, some weren't doing it and resulted in
failure if run in different order.

Close #948

Oid is defined as unsigned 32. On some Python implementations (probably
the ones where maxint = 2 ** 31) this can cause int overflow for large
values (see #961). On my 64 box it doesn't seem the case.

Oid handling was sloppy here and there (messages, casts...): trying to
use uint everywhere, and added a couple of helper macros to treat Oid
consistently.

Close #961.

This avoids the need to juggle with exceptions in order to scrub the
password after a connection error, which may also swallow signals
(see #898).