examples/default: use periph/rtc instead of rtc

The rtc module is deprecated and will be removed.

examples/default/Makefile

@@ -37,6 +37,7 @@ USEMODULE += vtimer
 USEMODULE += defaulttransceiver
 
 FEATURES_OPTIONAL += transceiver
+FEATURES_OPTIONAL += periph_rtc
 
 ifneq (,$(filter msb-430,$(BOARD)))
 	USEMODULE += sht11

examples/default/main.c

@@ -31,6 +31,10 @@
 #include "shell_commands.h"
 #include "board_uart0.h"
 
+#if FEATURE_PERIPH_RTC
+#include "periph/rtc.h"
+#endif
+
 #ifdef MODULE_LTC4150
 #include "ltc4150.h"
 #endif
@@ -156,6 +160,10 @@ int main(void)
     init_transceiver();
 #endif
 
+#ifdef FEATURE_PERIPH_RTC
+    rtc_init();
+#endif
+
     (void) puts("Welcome to RIOT!");
 
     shell_init(&shell, NULL, UART0_BUFSIZE, shell_readc, shell_putchar);