AP_HAL_PX4: Handle scripting priority

libraries/AP_HAL_PX4/Scheduler.cpp

@@ -418,6 +418,7 @@ bool PX4Scheduler::thread_create(AP_HAL::MemberProc proc, const char *name, uint
         { PRIORITY_IO, APM_IO_PRIORITY},
         { PRIORITY_UART, APM_UART_PRIORITY},
         { PRIORITY_STORAGE, APM_STORAGE_PRIORITY},
+        { PRIORITY_SCRIPTING, APM_SCRIPTING_PRIORITY},
     };
     for (uint8_t i=0; i<ARRAY_SIZE(priority_map); i++) {
         if (priority_map[i].base == base) {

libraries/AP_HAL_PX4/Scheduler.h

@@ -23,6 +23,7 @@
 #define APM_SHELL_PRIORITY       57
 #define APM_OVERTIME_PRIORITY    10
 #define APM_STARTUP_PRIORITY     10
+#define APM_SCRIPTING_PRIORITY    1
 
 /* how long to boost priority of the main thread for each main
    loop. This needs to be long enough for all interrupt-level drivers