Checksum code has been refactored to isolate common component
Added young checksum (faster than old one) selectable by Makefile
Fix for commit: Added young checksum (faster than old one) selectable by Makefile

Previous commit wich does not contains the modification of file pico_frame.c
Refactoring of frame send, avoid discarding when dev is busy
Fix: packet that already have eth header set need a shortcut to get out
Merge branch 'young' into pktout_refactoring
Increased default socket size to 6KB
When GCC is the compiler, use builtin endianess conversion.

Fixes #206
Fixed compilation without udp
Merge pull request #205 from tass-belgium/development

Development branch: QA, please consider for merging