sdl12-compat: README: Document SDL12COMPAT_NO_QUIT_VIDEO

From bb2f7ff398e3f1e75edfd7719f278e7aa4ba53d5 Mon Sep 17 00:00:00 2001
From: David Gow <[EMAIL REDACTED]>
Date: Sun, 21 Jan 2024 21:23:12 +0800
Subject: [PATCH] README: Document SDL12COMPAT_NO_QUIT_VIDEO

This hint was never documented in README.md, even though it was used in
a quirk, and mentioned briefly in COMPATIBILITY.md.

Fixes #329
---
 README.md | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/README.md b/README.md
index 434db4069..443574245 100644
--- a/README.md
+++ b/README.md
@@ -269,6 +269,11 @@ The available options are:
   backends, because SDL 1.2 didn't have wide support for its SysWM APIs
   outside of Windows and X11 anyhow.
 
+- SDL12COMPAT_NO_QUIT_VIDEO: (checked during SDL_QuitSubsystem)
+  If enabled, SDL_Quit() and SDL_QuitSubsystem() will never shut down the
+  video subsystem. This works around buggy applications which try to use
+  the video subsystem after shutting it down.
+
 
 # Compatibility issues with OpenGL scaling