Allow users to disable -Werror at configure time

Some users and distro packagers might not want to build with -Werror,
this allows them to disable using -Werror but enables it in the default
case so as to maintain the current behavior.
Merge pull request #63 from cardoe/werror

Allow users to disable -Werror at configure time
Next to BUS RESET, also accept NEXUS LOSS unit attention after login

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Retry RESERVE6/RELEASE6 upon BUS RESET UA

Signed-off-by: Bart Van Assche <bvanassche@acm.org>