[mythtv] DVB-C service description tables

[Roger James]

I knew that messing with this would come back to bite me. There is a hack 
in DVBStreamdata to handle the misuse of the the Service Description 
(other) table to transmit the data for the actual (currently tuned) stream. 
I need to improve the handling of this in my new SI code. To help me do 
this, can anyone explain to me why some cable providers feel the need to 
break the DVB spec in this way, or point me at any info about it.

Roger