EBML updates:

- AV1 support
- Support for outputting fragments longer than 30 seconds in duration
- Fixed FireFox support for Opus audio tracks
- Added support for stdin live input of EBML
- Fixed broken timestamps when seeking in VoD EBML files
- Analyser now calculates offsets for (manual) double-checking
- Added JSON track support to EBML input and output
- Added basic input support for SRT/ASS/SSA subtitles
- Opus CODECDELAY now actually calculated.
- Fixed Opus in Firefox
- Improved MP3 support, more robust handling of corruption, support for non-standard timescale sources

# Conflicts:
#	src/output/output_ebml.cpp

lib/ebml.h

@@ -48,6 +48,8 @@ namespace EBML{
     EID_PIXELWIDTH = 0x30,
     EID_FLAGLACING = 0x1C,
     EID_PIXELHEIGHT = 0x3A,
+    EID_DISPLAYWIDTH = 0x14B0,
+    EID_DISPLAYHEIGHT = 0x14BA,
     EID_TRACKNUMBER = 0x57,
     EID_CODECPRIVATE = 0x23A2,
     EID_LANGUAGE = 0x2B59C,
@@ -72,6 +74,9 @@ namespace EBML{
     EID_CUETRACKPOSITIONS = 0x37,
     EID_CUETIME = 0x33,
     EID_CUEPOINT = 0x3B,
+    EID_TAGS = 0x254c367,
+    EID_CODECDELAY = 0x16AA,
+    EID_SEEKPREROLL = 0x16BB,
     EID_UNKNOWN = 0
   };