stats: Fix build on FreeBSD

include stdint.h for int64_t and use netinet/in.h and not
netinet/ip.h for getting sockaddr_in and such.
diff --git a/include/osmocom/core/stats.h b/include/osmocom/core/stats.h
index 731fdb9..362d3fb 100644
--- a/include/osmocom/core/stats.h
+++ b/include/osmocom/core/stats.h
@@ -22,6 +22,8 @@
 #include <sys/socket.h>
 #include <osmocom/core/linuxlist.h>
 
+#include <stdint.h>
+
 struct msgb;
 struct osmo_stat_item_group;
 struct osmo_stat_item_desc;