build: W600-SDK importiert, Firmware-Build und Hello am EVK

Docker-Build mit gcc-arm-none-eabi 4.9-2014q4 (statt Homebrew-Cask) verwendet,
Dockerfile/tools/docker.sh dafür aus Task 13 vorgezogen. cmake/sdk.cmake schont
gcc 4.9 (kennt -fcommon/-Wno-error=... nicht). Zwei zusätzliche SDK-Stubs
(EarlyInit, pre_gpio_config) in src/sys/sdk_stubs.c ergänzt, siehe sdk/PATCHES.md.

sdk/Src/Network/lwip2.0.3/FILES

@@ -0,0 +1,15 @@
+api/      - The code for the high-level wrapper API. Not needed if
+            you use the lowel-level call-back/raw API.
+
+apps/     - Higher layer applications that are specifically programmed
+            with the lwIP low-level raw API.
+
+core/     - The core of the TPC/IP stack; protocol implementations,
+            memory and buffer management, and the low-level raw API.
+
+include/  - lwIP include files.
+
+netif/    - Generic network interface device drivers are kept here.
+
+For more information on the various subdirectories, check the FILES
+file in each directory.