Tools: sim_vehicle.py: use gps functions from pymavlink rather than MAVProxy

This should solve a problem on Windows where MAVProxy's libraries may
not be generally available (packed into a .exe)

Tools/autotest/sim_vehicle.py

@@ -22,7 +22,7 @@ import textwrap
 import time
 import shlex
 
-from MAVProxy.modules.lib import mp_util
+from pymavlink import mavextra
 from pysim import vehicleinfo
 
 # List of open terminal windows for macosx
@@ -407,10 +407,10 @@ def find_new_spawn(loc, file_path):
                     (instance, offset) = lines.split("=")
                     if ((int)(instance) == (int)(cmd_opts.instance)):
                         (x, y, z, head) = offset.split(",")
-                        g = mp_util.gps_offset((float)(lat), (float)(lon), (float)(x), (float)(y))
+                        g = mavextra.gps_offset((float)(lat), (float)(lon), (float)(x), (float)(y))
                         loc = str(g[0])+","+str(g[1])+","+str(alt+z)+","+str(head)
                         return loc
-        g = mp_util.gps_newpos((float)(lat), (float)(lon), 90, 20*(int)(cmd_opts.instance))
+        g = mavextra.gps_newpos((float)(lat), (float)(lon), 90, 20*(int)(cmd_opts.instance))
         loc = str(g[0])+","+str(g[1])+","+str(alt)+","+str(heading)
         return loc