shrecord: write to stream ringbuffer, not file
shrecord: write to stream ringbuffer, not file

Each client connection starts reading from the ringbuffer for that
encoded stream; each encoder writes continuously to that buffer.

Tested with dual encode (vga+cif) from a single camera, with the
following two stanzas in /etc/sighttpd/sighttpd.conf:

<SHRecord>
        Path "/video0/vga.264"
        CtlFile "/usr/share/shcodecs-record/k264-v4l2-vga-stream.ctl"
</SHRecord>

<SHRecord>
        Path "/video0/cif.264"
        CtlFile "/usr/share/shcodecs-record/k264-v4l2-cif-stream.ctl"
</SHRecord>

kfish/sighttpd,kfish/sighttpd