* stream.h: Add comment about the special zero-ing ability of
stream_put.
(stream_recvmsg, stream_write) should return ssize_t and size_t
respectively. Should both be extern linkage.
(stream_recvfrom) Stream aware wrapper around recvfrom, in style
of stream_read_try.
* stream.c: (stream_recvfrom) new function, wrapper around recvfrom.
(stream_recvmsg, stream_write) ssize_t and size_t return values