CommonDefaults: enable terrain in Auto and Guided

Without this, Auto and Guided ignore terrain-frame commands. This does
NOT force terrain following on for relative-frame commands.

At the time of writing, Mission Planner only sends relative frame for
Guided mode, but this parameter change means that I can fix that in the
future without needing to update the firmware.

SW-159

libraries/AP_HAL_ChibiOS/hwdef/CarbonixCommon/defaults.parm

@@ -165,3 +165,4 @@ SERVO8_MIN,1000
 SERVO9_FUNCTION,94 # Scripting function for LEDs
 SERVO9_MAX,2000
 SERVO9_MIN,1000
+TERRAIN_FOLLOW,72 # Enabled Auto and Guided (the command being executed must have the terrain frame though)