No extended header supported

[rstemmer]

I never saw a file found two files that used the extended ID3 header feature. This issue is just to keep track of the limitation.

Feel free to comment when this becomes a real issue.

Flags to implement:

• ID3v2.3.0
  • [X] none - Jump over header
  • [X] x - CRC data present
• ID3v2.4.0
  • [X] none - Jump over header
  • [X] b - Tag is an update
  • [X] c - CRC data present
  • [ ] d - Tag restrictions

[rstemmer]

Possible new command line option:

• --add-crc: Adds an extended header with CRC information or update check sum.
• --check-crc: Only check if the CRC sum is valid and then exit

[rstemmer]

--add-crc implemented as well as reading and writing extended header with CRC check sum. Currently available on the extheader branch