Oggenc division by zero issue

A crafted WAV file with number of channels set to 0 will cause oggenc to crash due to a division by zero issue at :

Stopped reason: SIGFPE 0x0804d497 in wav_open (in=0x805c368, opt=0xbffff2ec, oldbuf=0x805c4d0 "RIFF\f\002", buflen=0xc) at audio.c:552 552 opt->total_samples_per_channel = len/(format.channels*samplesize);

Tests were performed using vorbis-tools 1.4.0