Fix missing stdint.h declarations if mgos_dht.h is the first include in client app (#5)

* Add missing include

* Move stdint.h in mgos_dht.h

Author: nliviu

include/mgos_dht.h

@@ -26,6 +26,7 @@
 
 #include <math.h>
 #include <stdbool.h>
+#include <stdint.h>
 
 #ifdef __cplusplus
 extern "C" {

src/mgos_dht.c

@@ -20,7 +20,6 @@
  * [mgos_dht.c](https://github.com/mongoose-os-libs/dht/blob/master/src/mgos_dht.c)
  */
 
-#include <stdint.h>
 #include "mgos_dht.h"
 #include "mgos_gpio.h"
 #include "mgos_hal.h"