AP_HAL: use noreturn attribute on panic

should reduce coverity warnings

libraries/AP_HAL/AP_HAL_Macros.h

@@ -17,4 +17,6 @@
 # define constexpr const
 #endif
 
+#define NORETURN __attribute__ ((noreturn))
+
 #endif // __AP_HAL_MACROS_H__

libraries/AP_HAL/Scheduler.h

@@ -54,7 +54,7 @@ public:
     virtual bool     system_initializing() = 0;
     virtual void     system_initialized() = 0;
 
-    virtual void     panic(const prog_char_t *errormsg) = 0;
+    virtual void     panic(const prog_char_t *errormsg) NORETURN = 0;
     virtual void     reboot(bool hold_in_bootloader) = 0;
 
     /**

libraries/AP_HAL_AVR/Scheduler.h

@@ -45,7 +45,7 @@ public:
     bool     system_initializing();
     void     system_initialized();
 
-    void     panic(const prog_char_t *errormsg);
+    void     panic(const prog_char_t *errormsg) NORETURN;
     void     reboot(bool hold_in_bootloader);
 
     void     set_timer_speed(uint16_t timer_hz);

libraries/AP_HAL_Empty/Scheduler.h

@@ -32,7 +32,7 @@ public:
     bool     system_initializing();
     void     system_initialized();
 
-    void     panic(const prog_char_t *errormsg);
+    void     panic(const prog_char_t *errormsg) NORETURN;
     void     reboot(bool hold_in_bootloader);
 
 };

libraries/AP_HAL_FLYMAPLE/Scheduler.h

@@ -53,7 +53,7 @@ public:
     bool     system_initializing();
     void     system_initialized();
 
-    void     panic(const prog_char_t *errormsg);
+    void     panic(const prog_char_t *errormsg) NORETURN;
     void     reboot(bool hold_in_bootloader);
 
 private:

libraries/AP_HAL_Linux/Scheduler.h

@@ -43,7 +43,7 @@ public:
     bool     system_initializing();
     void     system_initialized();
 
-    void     panic(const prog_char_t *errormsg);
+    void     panic(const prog_char_t *errormsg) NORETURN;
     void     reboot(bool hold_in_bootloader);
 
     void     stop_clock(uint64_t time_usec);

libraries/AP_HAL_PX4/Scheduler.h

@@ -59,7 +59,7 @@ public:
     void     suspend_timer_procs();
     void     resume_timer_procs();
     void     reboot(bool hold_in_bootloader);
-    void     panic(const prog_char_t *errormsg);
+    void     panic(const prog_char_t *errormsg) NORETURN;
 
     bool     in_timerprocess();
     bool     system_initializing();

libraries/AP_HAL_SITL/Scheduler.h

@@ -37,7 +37,7 @@ public:
     void     system_initialized();
 
     void     reboot(bool hold_in_bootloader);
-    void     panic(const prog_char_t *errormsg);
+    void     panic(const prog_char_t *errormsg) NORETURN;
 
     bool     interrupts_are_blocked(void) {
         return _nested_atomic_ctr != 0;

libraries/AP_HAL_VRBRAIN/Scheduler.h

@@ -39,7 +39,7 @@ public:
     void     suspend_timer_procs();
     void     resume_timer_procs();
     void     reboot(bool hold_in_bootloader);
-    void     panic(const prog_char_t *errormsg);
+    void     panic(const prog_char_t *errormsg) NORETURN;
 
     bool     in_timerprocess();
     bool     system_initializing();