#3 fails to compile on amd64

[Perry Lorier]

libjingle fails to compile on an amd64 due to the
prototype of VoiceChannel::SendPacket() being:
void VoiceChannel::SendPacket(const void *data, size_t
len);
and the implementation being:
void VoiceChannel::SendPacket(const void *data,
unsigned int len);

on amd64, size_t is not an "unsigned int". The fix is
to change talk/session/phone/voicechannel.cc to have
"size_t" as the type of the last parameter instead of
"unsigned int".