strcat(2): fix strchr() and strrchr() function prototypes (thanks BurnZeZ)
9boot(8): -from
ethervirtio: avoid dumping packets in txproc when ring gets full
ethervirtio: implement promisc and multicast mode, cleanup

add vctlcmd() function to setup and comlete control commands.
handle Vctlq and implement promiscuous and multicast mode commands.
remove Vqueue.block[] and Vqueue.header. these are not properties
of the queue (Vctlq as no block array).

the block[] array only needs to be half the queue size as we use
two descriptors per packet.

fix broken shutdown() and remove useless ctl() function.
ethervirtio: fix missing */