Native error code never passed to DBI

[M-Ostheimer]

Excerpt from pod/DBD::ODBC#odbc_getdiagrec:

odbc_getdiagrec

:

All of the state, native and message text are already passed to DBI
via its set_err method so this method does not really tell you
anything you cannot already get from DBI except when there is more
than one diagnostic.

This is not correct, because all calls of DBIh_SET_ERR_ get as argument err passed a 1 or 0 ❌