update copyright info

update license to GPLv2 and GPLv3

Fix warnings in debug build

Separate debug defines for every module

pico_tree_insert: check return value and free memory if needed

Issue #387: Added some more checking/freeing stuff/todos

Issue #387: Check return value of pico_timer_add() and pico_timer_add_hashed()

Coverity ID 141541: ETH/ARP: Make sure frame is discarded in
pico_ethernet_receive on failure
This allows to remove the pico_discard_frame in pico_ethsend_local to
avoid a possible double free

fixing pico_tree_insert return value checking (issue #380)

[ARP] - Removed redundant copying of frame on postponing

[Ethernet] - Fixed typos

[Ethernet] - Full PoC of seperation of ethernet in standalone protocols with its own queues and its own protocol definition.

Seperation of ethernet from the stack

Make local variables static

detected using -Wmissing-variable-declarations clang option

Enforced style via uncrustify

Fixed bug in ARP: when a host is marked unreachable, the corresponding
frames in the queue were being freed twice.

make SLAACv4 detect simultaneous probe conflicts

Revamping timer API to fix #308

Improved C89 compatability (e.g. Watcom compiler)

fix for ipv4 frag sender

pico_arp_queued_trigger: Free allocated frames after sending it

Added -Wmissing-prototypes, some signature changed.

Updated Copyright information.

Refactoring of frame send, avoid discarding when dev is busy

Refactored picoapp

Refactoring of ARP, IPV6 neighbors, packet delivery.

Refactored IP address comparison into one centralized function

Forgotten __attribute__((packed)) in arp.c

Coding style fixes

ARP: a bit of refactoring, should also fix #101

Again, reducing code complexity

Reduce complexity of arp module (minor changes)

Try to further decrease code complexity in the ARP module

Refactoring of arp module

Moved ARP support into IPV4 submodule.