Add missing includes

The headers were implicitly included recursively, but make it explicit.

app/src/main.c

@@ -1,6 +1,7 @@
 #include "common.h"
 
 #include <stdbool.h>
+#include <stdio.h>
 #ifdef HAVE_V4L2
 # include <libavdevice/avdevice.h>
 #endif

app/src/util/net.c

@@ -2,6 +2,7 @@
 
 #include <assert.h>
 #include <stdio.h>
+#include <stdlib.h>
 
 #ifdef _WIN32
 # include <ws2tcpip.h>