examples: make includes adhere to coding conventions

examples/default/main.c

@@ -32,11 +32,11 @@
 #include "board_uart0.h"
 
 #ifdef MODULE_LTC4150
-#include <ltc4150.h>
+#include "ltc4150.h"
 #endif
 
 #ifdef MODULE_TRANSCEIVER
-#include <transceiver.h>
+#include "transceiver.h"
 #endif
 
 #define SND_BUFFER_SIZE     (100)

examples/ipc_pingpong/main.c

@@ -19,9 +19,10 @@
  */
 
 #include <stdio.h>
-#include <thread.h>
-#include <msg.h>
-#include <kernel.h>
+
+#include "thread.h"
+#include "msg.h"
+#include "kernel.h"
 
 void second_thread(void)
 {