Move the OBSTACLE_BUFFER define to mtp.h. Add a hack to deal with

goal's in obstacles: move towards the edge of the exclusion zone where
the path intersects and wait before trying again; if the obstacle is a
robot, move to the edge perpendicular to the robot to clear the way
for the other guy.

robots/mtp/mtp.h

@@ -475,6 +475,14 @@ int mtp_obstacle_config_invariant(struct obstacle_config *oc);
  */
 void mtp_print_packet(FILE *file, struct mtp_packet *mp);
 
+/**
+ * The size of the buffer zone around the obstacles, in meters.
+ *
+ * XXX This is for the garcia's only.  Other robots will require different
+ * buffer sizes.
+ */
+#define OBSTACLE_BUFFER 0.23f
+
 #ifndef min
 #define min(x, y) (((x) < (y)) ? (x) : (y))
 #endif