Merge pull request #33 from supramaterial/feature-encX24J600-wip

Feature enc x24 j600 wip
Fix ENCX24J600 packet sending
Fix a packet reading bug in ENCX24J600 driver
Add memory.c to this branch
Add debugging output to ARP and Ethernet
Add __udp_sockets and __coap_urls to STM32F334 linker script
Cosmetic fixes to comments
Temporary fix to compile CoAP with ENCX28J600
Add test_CoAP_no_threads test case