Merge pull request #4900 from OlegHahm/libcoap_dep

libcoap: fix missing dependencies and includes

Makefile.dep

@@ -3,6 +3,7 @@ include $(RIOTBASE)/drivers/Makefile.dep
 
 ifneq (,$(filter libcoap,$(USEPKG)))
     USEMODULE += posix_sockets
+    USEMODULE += gnrc_conn_udp
 endif
 
 ifneq (,$(filter nhdp,$(USEMODULE)))

sys/posix/sockets/posix_sockets.c

@@ -31,6 +31,16 @@
 #include "sys/socket.h"
 #include "netinet/in.h"
 
+#ifdef  MODULE_CONN_IP
+#   include "net/conn/ip.h"
+#endif  /* MODULE_CONN_IP */
+#ifdef  MODULE_CONN_TCP
+#   include "net/conn/tcp.h"
+#endif  /* MODULE_CONN_TCP */
+#ifdef  MODULE_CONN_UDP
+#   include "net/conn/udp.h"
+#endif  /* MODULE_CONN_UDP */
+
 #define SOCKET_POOL_SIZE    (4)
 
 /**