Use native image APIs on MS-Windows by default

* src/w32term.c (syms_of_w32term) <w32-use-native-image-API>: Now
t by default on W2K and later systems, but only on WINDOWSNT
builds.

* etc/NEWS: Announce the change.

etc/NEWS

@@ -1821,6 +1821,19 @@ follow the system's dark mode: GUI frames use the appropriate light or
 dark title bar and scroll bars, based on the user's Windows-wide color
 settings.
 
+---
+*** Emacs now uses native image APIs to display some image formats.
+On Windows 2000 and later, Emacs now defaults to using the native
+image APIs for displaying the BMP, GIF, JPEG, PNG, and TIFF images.
+This means Emacs on MS-Windows needs no longer use external image
+support libraries to display those images.  Other image types -- XPM,
+SVG, and WEBP -- still need support libraries for Emacs to be able to
+display them.
+
+The use of native image APIs is controlled by the variable
+'w32-use-native-image-API', whose value now defaults to t on systems
+where those APIs are available.
+
 +++
 *** Emacs now supports display of BMP images using native image APIs.
 When 'w32-use-native-image-API' is non-nil, Emacs on MS-Windows now

src/w32term.c

@@ -7744,9 +7744,10 @@ The native image API library used is GDI+ via GDIPLUS.DLL.  This
 library is available only since W2K, therefore this variable is
 unconditionally set to nil on older systems.  */);
 
-  /* For now, disabled by default, since this is an experimental feature.  */
-#if 0 && HAVE_NATIVE_IMAGE_API
-  if (os_subtype == OS_9X)
+  /* Disabled for Cygwin/w32 builds, since they don't link against
+     -lgdiplus, see configure.ac.  */
+#if defined WINDOWSNT && HAVE_NATIVE_IMAGE_API
+  if (os_subtype == OS_SUBTYPE_9X)
     w32_use_native_image_api = 0;
   else
     w32_use_native_image_api = 1;