These streams are reported as seekable, but all tests show they are not,
and the server merely pretends the streams are seekable. The server
responds with:

    content-range: bytes 0-1999999999/2000000000

Range requests seem to be correctly answered, but the actual data
returned at the same offset is different. Assume this is a bug in the
server software. The server identifies itself as:

    Server: MediaGateway 3.5.2-001

Add a hack that checks the server name, and disables seeking in this
case.

Test URL: http://8283.live.streamtheworld.com:80/CBC_R1_VCR_H_SCSigned-off-by: Michael Niedermayer <michaelni@gmx.at>