bugfix: set new random value when more than sizeof(v) bytes are requested
bugfix: set new random value when more than sizeof(v) bytes are requested

The function contiki_prng_impl() used to fill the entire buffer with the
same two bytes of random data. (Thanks to Andreas Bender for pointing out.)

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