textproc/re-flex: update to 1.3.8 which includes performance improvements
Release notes:
https://github.com/Genivia/RE-flex/releases/tag/v1.3.5
https://github.com/Genivia/RE-flex/releases/tag/v1.3.6
https://github.com/Genivia/RE-flex/releases/tag/v1.3.7
https://github.com/Genivia/RE-flex/releases/tag/v1.3.8