Renamed error_message and warning_message macros.

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"

Extras/InverseDynamics/RandomTreeCreator.cpp

@@ -47,7 +47,7 @@ int RandomTreeCreator::getBody(const int body_index, int* parent_index, JointTyp
             *joint_type = FLOATING;
             break;
         default:
-            error_message("randomInt() result out of range\n");
+            bt_id_error_message("randomInt() result out of range\n");
             return -1;
     }