Update appveyor to force modern VS version.

Sibras · Sibras · commit 744965c7f3cf · 2024-11-02T17:17:45.000+11:00
The default VS2015 was miscompiling the code.
diff --git a/appveyor.yml b/appveyor.yml
@@ -6,6 +6,8 @@ branches:
 skip_non_tags: true
 shallow_clone: true
 
+image: Visual Studio 2022
+
 configuration: Release
 
 platform:
