luminais

Results 3 issues of luminais

https://github.com/obgm/libcoap/blob/1d484849e881d6d2eb5099e189d85b84d995ac25/src/net.c#L472-L477 https://github.com/obgm/libcoap/blob/1d484849e881d6d2eb5099e189d85b84d995ac25/src/coap_io_lwip.c#L105-L128

if the parameter'size' of function coap_new_string is not smaller than MEMP_LEN_COAPSTRING, it will leading to memory out-of-bounds write