error_message and warning_message are common strings that are likely to
collide. Renamed to bt_id_{error,warning}_message to more strongly
uniquify.
grep -r error_message -l src/BulletInverseDynamics | \
xargs sed -i -e "s/error_message/bt_id_error_message/g"
grep -r warning_message -l src/BulletInverseDynamics | \
xargs sed -i -e "s/warning_message/bt_id_warning_message/g"
3f03b41091