AC_Fence: add build_options.py option to remove fencepoint protocol

also gate more code on defines

Saves ~2kB

libraries/AC_Fence/AC_Fence_config.h

@@ -9,3 +9,7 @@
 #ifndef AP_FENCE_ENABLED
 #define AP_FENCE_ENABLED 2
 #endif
+
+#ifndef AC_POLYFENCE_FENCE_POINT_PROTOCOL_SUPPORT
+#define AC_POLYFENCE_FENCE_POINT_PROTOCOL_SUPPORT AP_FENCE_ENABLED
+#endif

libraries/AC_Fence/AC_PolyFence_loader.cpp

@@ -1221,7 +1221,6 @@ bool AC_PolyFence_loader::write_fence(const AC_PolyFenceItem *new_items, uint16_
 }
 
 
-#if AC_POLYFENCE_FENCE_POINT_PROTOCOL_SUPPORT
 bool AC_PolyFence_loader::get_return_point(Vector2l &ret)
 {
     if (!check_indexed()) {
@@ -1296,7 +1295,6 @@ bool AC_PolyFence_loader::get_return_point(Vector2l &ret)
 
     return true;
 }
-#endif
 
 AC_PolyFence_loader::FenceIndex *AC_PolyFence_loader::find_first_fence(const AC_PolyFenceType type) const
 {

libraries/AC_Fence/AC_PolyFence_loader.h

@@ -39,8 +39,6 @@ public:
 #include <AP_Common/Location.h>
 #include <GCS_MAVLink/GCS_MAVLink.h>
 
-#define AC_POLYFENCE_FENCE_POINT_PROTOCOL_SUPPORT 1
-
 class AC_PolyFence_loader
 {
 
@@ -174,12 +172,10 @@ public:
     // call @10Hz to check for fence load being valid
     void update();
 
-#if AC_POLYFENCE_FENCE_POINT_PROTOCOL_SUPPORT
     // get_return_point - returns latitude/longitude of return point.
     // This works with storage - the returned vector is absolute
     // lat/lon.
     bool get_return_point(Vector2l &ret) WARN_IF_UNUSED;
-#endif
 
     // return total number of fences - polygons and circles
     uint16_t total_fence_count() const {