qerror: qerror_table: don't use C99 struct initializers

This allows for changing QERR_ macros to initialize two struct members
at the same time. See next commit for more details.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
