Log Message:
Update to 3.51. From the changelog:

- SVG output: added `white-space: pre` in styles
- HTML output: replaced ' by ' (https://bugs.debian.org/927410)
- HTML output: fixed index file format (missing close tags)
- CLI: moved syntax recognition functions to DataDir class
- CLI: added regular expressions and default false values to --verbose output
- CLI: fixed `--list-cat` without `--list-scripts` \ 
(https://gitlab.com/saalen/highlight/issues/107)
- CLI: added optional argument to `--base16` \ 
(https://gitlab.com/saalen/highlight/issues/113)
- CLI: added default base16 themes (https://gitlab.com/saalen/highlight/issues/113)
- CLI: added `--isolate` option (https://gitlab.com/saalen/highlight/issues/118)
- GUI: improved UTF16 input path handling on Windows