init static PDU buffers; bugfixes
init static PDU buffers; bugfixes

fredericgermain/libcoap,sgso/libcoap,thecodemaiden/libcoap-fork,thecodemaiden/libcoap-fork,joaopedrotaveira/libcoap,joaopedrotaveira/libcoap,alexaring/libcoap,sgso/libcoap,RIOT-OS/libcoap,markushx/libcoap,gebart/libcoap,joaopedrotaveira/libcoap,pabigot/libcoap,authmillenon/libcoap,OlegHahm/libcoap,nmacs/libcoap,OlegHahm/libcoap,fredericgermain/libcoap,alexaring/libcoap,RIOT-OS/libcoap,nmacs/libcoap,alexaring/libcoap,markushx/libcoap,nmacs/libcoap,authmillenon/libcoap,gebart/libcoap,PolymorhicCode/libcoap,pabigot/libcoap,fredericgermain/libcoap,sgso/libcoap,gebart/libcoap,OlegHahm/libcoap,pabigot/libcoap,authmillenon/libcoap,markushx/libcoap