[mythtv-cmyth] Handles extended TS stream: M2TS, ATSC 8-VSB, ISDB-T, DVB-T/C/S

- M2TS packet size is 192 bytes: 4B for timer + MTS packet
- ATSC 8-VSB packet size is 208: MTS packet + 20B for FEC
- ISDB-T packet size is 204: MTS packet + 16B for FEC
- DVB-T/C/S packet size is 204: MTS packet + 16B for FEC

At first synchro it check TS stream and select packet size after reaching the best score.
Reached score varies from 2 (TS_CHECK_MIN_SCORE) to 10 packets (...MAX_SCORE),
depending of collisions (norme use 624 packets for QOS).
Encapsulated TS packet is not affected ans keep original size of 188 bytes. Once packet
size is discovered, function GoNext() will move to sync byte of next TS packet and will
discard unused data using selected size. Also it allows to check stream at startup and
break it if invalid returning AVCONTEXT_TS_NOSYNC.
[mythtv-cmyth] Cosmetics in elementaryStream.cpp
[mythtv-cmyth] Fix compilation warning for OSX/IOS
[mythtv-cmyth] Fix channel icon download with 0.27 backend

The default location is defined in the built-in ChannelIcons Storage Group.
When full path is specified then location is not considered by backend: This fix runs with older backend.
[mythtv-cmyth] Toggle Show/hide not recording

Function MythScheduleManager::ToggleShowNotRecording() allows to enable or disable visibility of not recording rules.
In the future user could use a new hook to enable or disable visibility and then manage not recording rules.
[mythtv-cmyth] Manage special recording rules

Manage "Not recording" rules with PVR timer screen:
- Add setting menu hook "Show/Hide not recording rules"

New functions to make and break a broadcast UID for program

Create special recording rules:
- Add EPG menu hook "Record all showings (this channel)"
- Add EPG menu hook "Record this showing every week"
- Add EPG menu hook "Record this showing every day"
- Add EPG menu hook "Record one showing (all channels)"
- Add EPG menu hook "Record new episodes (this channel)"