[mythtv] DVB SI rework

[Roger James]

I have pushed the latest version up to Github rogerjames99/mythtv. This 
fixes some mutex deadlocks and adds static caches of SD and EI table 
sections, md5 hashes to check for table version wrap around. There are 
still problems with SD table handling when channel scanning that I have not 
looked at yet.

I am running a soak test overnight to check for memory leaks using the GNU 
leak sanitizer. This requires an update to mythsettings.pro that I have 
pushed up to Github.

Roger