SDL_image: upgrade vendored libpng to 1.6.52 (596b6)

From 596b6bb124ebbb12357dfeb36d353277b3e20b88 Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Thu, 4 Dec 2025 02:10:50 +0300
Subject: [PATCH] upgrade vendored libpng to 1.6.52

---
 .gitmodules     | 2 +-
 external/libpng | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/.gitmodules b/.gitmodules
index 56f7f1d7..3b95fd04 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -5,7 +5,7 @@
 [submodule "external/libpng"]
 	path = external/libpng
 	url = https://github.com/libsdl-org/libpng.git
-	branch = v1.6.51-SDL
+	branch = v1.6.52-SDL
 [submodule "external/libwebp"]
 	path = external/libwebp
 	url = https://github.com/libsdl-org/libwebp.git
diff --git a/external/libpng b/external/libpng
index efecf112..8c1f718d 160000
--- a/external/libpng
+++ b/external/libpng
@@ -1 +1 @@
-Subproject commit efecf1124f248dd325925bb7978f7f66f373541a
+Subproject commit 8c1f718d0fb56a2c04aca6115ce108e3da8df7a6