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"