Improve analog tuner signal strength and quality reporting.
Stream type values defined with #define must be compatible with byte (unsigned char) storage. That means no negative values!
Set context for extension loading for analog tuners.
Fix "use of obsolete..." warning.
Rearrange MPEG 2 subchannel code a little; no functional changes. I thought I was going to need to override some functions but it turned out to be unnecessary.
Avoid deadlocks in the PMT grabber, and fix case where the grabber selects the first program on behalf of TVE.
Fix RTL283x FM deadlock on PMT change, caused by attempting to call methods on TsWriter from within the callback. That won't work if TsWriter is in a STA. The STA is strictly single threaded, so the message queue doesn't get pumped until the callback finishes.