Build system: Raise warning level

Default esp-idf builds now show -Wextra warnings (except for a few:
signed/unsigned comparison, unused parameters, old-style C declarations.)

CI building of examples runs with that level raised to -Werror, to catch
those changes going into the main repo.

components/freertos/ringbuf.c

@@ -495,8 +495,8 @@ BaseType_t xRingbufferSend(RingbufHandle_t ringbuf, void *data, size_t dataSize,
                 //we will need to wait some more.
                 ticks_to_wait = ticks_end - xTaskGetTickCount();
             }
-        } while (ringbufferFreeMem(rb) < needed_size && ticks_to_wait>=0);
-        
+        } while (ringbufferFreeMem(rb) < needed_size && ticks_end >= xTaskGetTickCount());
+
         //Lock the mux in order to make sure no one else is messing with the ringbuffer and do the copy.
         portENTER_CRITICAL(&rb->mux);
         //Another thread may have been able to sneak its write first. Check again now we locked the ringbuff, and retry

components/freertos/tasks.c

@@ -2704,7 +2704,7 @@ void vTaskSwitchContext( void )
 		taskENTER_CRITICAL_ISR(&xTaskQueueMutex);
 		
 		unsigned portBASE_TYPE foundNonExecutingWaiter = pdFALSE, ableToSchedule = pdFALSE, resetListHead;
-		unsigned portBASE_TYPE uxDynamicTopReady = uxTopReadyPriority;
+		portBASE_TYPE uxDynamicTopReady = uxTopReadyPriority;
 		unsigned portBASE_TYPE holdTop=pdFALSE;
 		
 		/*
@@ -2717,8 +2717,6 @@ void vTaskSwitchContext( void )
 		
 		while ( ableToSchedule == pdFALSE && uxDynamicTopReady >= 0 )
 		{
-			configASSERT( uxTopReadyPriority>=0 );
-			configASSERT( uxDynamicTopReady>=0 );
 			resetListHead = pdFALSE;
 			// Nothing to do for empty lists
 			if (!listLIST_IS_EMPTY( &( pxReadyTasksLists[ uxDynamicTopReady ] ) )) {