Motivation / Problem

OpenTTD does not use gendered terms or pronouns in English. (See #8601/#8659 or search in english.txt).

On TT-Forums, tofu7 pointed out the single instance where we use "his/her" to refer to the player and noted that this is not inclusive for people who don't use binary pronouns, which according to a Trevor Project survey accounts for 25% of LGBTQ+ teens.

Tofu7:
I was setting up a dedicated server and noticed that when I changed my name as a client the server says "Client has changed his/her name..."

I think it would be better to change this to say "Client has changed their name..." as it is generally more inclusive of people who don't use he or she pronouns.

Description

This PR changes the single usage of "his/her" to "their".

"They/them/their" is a commonly-accepted gender-neutral pronoun both in the LGBTQ+ community and in the wider world. The Oxford English Dictionary reports its usage as early as 1375, and the BBC reports additional usage in The Canterbury Tales, Hamlet, and Pride and Prejudice. Today, it is widely used to refer to someone whose gender is not known, as in finding a lost umbrella and remarking, "someone lost their umbrella."

A 2019 Washington University study showed that use of gender-neutral pronouns reduce biases against women and LGBTQ+ people.

Limitations

Translations may need updating (depending on pronoun use in each language), but we just released 1.12 so I don't see a problem with this.

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker