Reporting missing or buggy detection

* Wanted: Reproducers and file format description

It's crucial to understand any mis-detection and being able to test
any fix, so please provide something suitable: Attach a short
sample, or send an information where to find it. Double-check this
file neither contains sensitive data nor infringes a copyright.

Also welcome: Pointers to documents that describe the file format.

* Suggested bug severities

  - Missing detection (just 'data'), or enhancements: wishlist
  - Mis-detection: normal
  - Overall correct detection, but with some errors: minor