TinyDTLS integrated to RIOT (without sockets)

- All the commits haven been squashed.
- The Makefile are upgraded for the lastet GNRC API version.
- Fixed errors for Travis and Murdock.

examples/dtls-echo/Makefile

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+# name of your application
+APPLICATION = dtls_echo
+
+# If no BOARD is found in the environment, use this default:
+BOARD ?= native
+
+# This has to be the absolute path to the RIOT base directory:
+RIOTBASE ?= $(CURDIR)/../..
+
+BOARD_INSUFFICIENT_MEMORY := airfy-beacon chronos msb-430 msb-430h nrf51dongle \
+                          nrf6310 nucleo-f103 nucleo-f334 pca10000 pca10005 spark-core \
+                          stm32f0discovery telosb weio wsn430-v1_3b wsn430-v1_4 \
+                          yunjia-nrf51822 z1 nucleo-f072
+
+# Include packages that pull up and auto-init the link layer.
+# NOTE: 6LoWPAN will be included if IEEE802.15.4 devices are present
+USEMODULE += gnrc_netdev_default
+USEMODULE += auto_init_gnrc_netif
+# Specify the mandatory networking modules for IPv6 and sUDP
+USEMODULE += gnrc_ipv6_router_default
+USEMODULE += gnrc_udp
+# Add a routing protocol
+USEMODULE += gnrc_rpl
+# This application dumps received packets to STDIO using the pktdump module
+USEMODULE += gnrc_pktdump
+# Additional networking modules that can be dropped if not needed
+USEMODULE += gnrc_icmpv6_echo
+# Add also the shell, some shell commands
+USEMODULE += shell
+USEMODULE += shell_commands
+USEMODULE += ps
+
+#This is from the original example, still not sure why is here.
+ifeq (,$(filter native,$(BOARD)))
+  USEMODULE += pthread
+endif
+
+# NOTE: Add the package for TinyDTLS
+USEPKG += tinydtls
+
+# Comment this out to disable code in RIOT that does safety checking
+# which is not needed in a production environment but helps in the
+# development process:
+CFLAGS += -DDEVELHELP
+
+# NOTE: Those are taken from TinyDTLS (As the original Makefiles are
+#      overwitten is a good idea to preserve them here.
+CFLAGS += -DDTLSv12 -DWITH_SHA256
+# NOTE: The configuration for socket or non-socket can be handled here.
+CFLAGS += -DWITH_RIOT_GNRC
+
+# Change this to 0 show compiler invocation lines by default:
+QUIET ?= 1
+
+include $(RIOTBASE)/Makefile.include

examples/dtls-echo/README.md

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+# dtls_echo
+
+This example  shows you how to use TinyDTLS with the non-socket approach.
+
+This code  is based on  ../gnrc_networking and ../gnrc_tftp.
+Is a good idea to read their README.md's for any doubt of how making the
+testings.
+
+## SOCKET vs. Non-socket (GNRC)
+
+This example is configured to use the GNRC instead of  sockets (over GNRC).
+At the moment, the configuration must be done manually in the Makefile of
+this project.
+
+## Fast configuration (Between RIOT instances):
+
+Preparing the logical interfaces:
+
+    ./../../dist/tools/tapsetup/tapsetup --create 2
+
+For the server instance:
+
+    make all; PORT=tap1 make term
+    dtlss start
+    ifconfig
+
+Do not forget to copy the IPv6 addresses!
+
+For the client:
+
+    PORT=tap0 make term
+    dtlsc <IPv6's server address> "DATA TO DATA TO DATA!"