Merge pull request #4414 from Memphiz/ios7airplayfix

[airplay] - fix regression introduced by ios7 clients
Merge pull request #4335 from Jalle19/change-default-level

Use FF_LEVEL_UNKNOWN by default (prevents some common mismatches in
Merge pull request #4337 from voguemaster/only_allow_extend_duration_real_streams

Do not allow non-content stream types to extend the format context's dur...
Merge pull request #4433 from FernetMenta/alsa

AE: add verbose logging, start with alsa logger
Merge pull request #4436 from ace20022/ext_sub_details

 [Ext. subs] Use ISO639-2 T language codes for external subtitles details.