[mythtvnz] mhegepgsnoop tuner support

[Stephen Worthington]

I have been looking at the tuner code in mhegepgsnoop and I think it
should be possible to make it work directly with HDHomerun tuners by
just running hdhomerun_config and redirecting its output to stdout, so
that mhegepgsnoop can read it.  Similarly, it seems that recent
versions of ffmpeg (>= 4.4?) can do the same for SAT>IP using a
"satip://" url.  So I think I will be refactoring the tuner code so
that I can make different tuner modules that interface to a standard
mhegepgsnoop interface.  Then I can add HDHomerun and SAT>IP tuner
modules as well as the existing supported input methods.  That would
mean there should be support for:

Normal /dev/dvb DVB-T tuners (PCIe, USB, ...)
HDHomerun DVB-T tuners
SAT>IP DVB-T tuners
Using dvbsnoop output
Reading from a pre-recorded transport stream (*.ts) file (as for Mike
Brady's method of handling HDHomerun tuners at present)

So, are there any other types of tuners out there that might need
support?  Is anyone using VBOX tuners, for example?

This is a fairly major change to mhegepgsnoop, so I will be releasing
it as version 0.8, and if there are any immediate fixes needed before
then I will do them as 0.7.x.  I may want to adjust the command line
options also, so it may not be 100% compatible with scripts using the
0.7.x versions.