AP_Scripting: added example script that causes a hard fault

this exercises rapid fault handling

libraries/AP_Scripting/examples/fault_handling.lua

@@ -0,0 +1,50 @@
+--[[
+   example script to test fault handling with pcall
+--]]
+
+local MAV_SEVERITY = {EMERGENCY=0, ALERT=1, CRITICAL=2, ERROR=3, WARNING=4, NOTICE=5, INFO=6, DEBUG=7}
+
+gcs:send_text(MAV_SEVERITY.INFO, "Loading fault test")
+
+local test_count = 0
+
+--[[
+   evaluate some lua code and return as a string
+--]]
+local function evaluate(code)
+   local eval_code = "function eval_func()\n" .. code .. "\nend\n"
+   local f, errloc, err = load(eval_code, "eval_func", "t", _ENV)
+   if not f then
+      gcs:send_text(MAV_SEVERITY.info, string.format("load failed: err=%s errloc=%s", err, errloc))
+      return nil
+   end
+   local success, err2 = pcall(f)
+   if not success then
+      gcs:send_text(MAV_SEVERITY.DEBUG,string.format("pcall failed: err=%s", err2))
+      return nil
+   end
+   local ok, s2 = pcall(eval_func)
+   eval_func = nil
+   if ok then
+      return s2
+   end
+   return nil
+end
+
+local function run_test()
+   evaluate("local loc = nil; loc:get_lat()")
+end
+
+local function update()
+   test_count = test_count + 1
+   if test_count % 100 == 0 then
+      gcs:send_text(MAV_SEVERITY.INFO,string.format("Test %u", test_count))
+   end
+   run_test()
+   return update,1
+end
+
+gcs:send_text(MAV_SEVERITY.INFO, "Starting fault test in 2 seconds")
+
+-- wait a while for GCS to connect
+return update,2000