Isabelle Santin

This PR addresses a key issue in the string conversion code for the `MagnetLink` class where the Exact Length `xl=` attribute would not be printed, even if the current instance...

This PR fixes https://github.com/alanmcgovern/monotorrent/issues/708 for OS platforms that use a forward-slash as their path separator character. Tested and working on Android and iOS platforms, Linux should be fine too.

### Describe the bug Exception: `Could not create glyphTypeface. Font family: $Default (key: ). Style: Normal. Weight: Normal. Stretch: Normal` Stack trace: ``` at Avalonia.Media.Typeface.get_GlyphTypeface() at Avalonia.Rendering.Composition.Compositor.get_DiagnosticTextRenderer() at Avalonia.Rendering.Composition.Compositor.CreateCompositionTarget(Func`1 surfaces)...

This PR makes minor changes to the FFMediaToolkit library to support the latest FFmpeg bindings for version 8.0.