Updated the ZX Spectrum emulator - Fuse.

- Implement PAL composite scaler chroma blending across lines
- GTK UI: add freely resizable, aspect-ratio-preserving display scaling and improved fullscreen behaviour
- GTK UI: preserve scaler families when resizing and prevent stale display borders
- GTK on Win32 UI: fix drag-and-drop file paths
- Fall back to default settings when loading a settings file fails
- Decode BASIC tokens and symbols in tape header names
- Wii UI: skip symbol characters
- Expand disassembler, debugger expression evaluator, and scaler test coverage
- Various minor bugfixes and cleanups