NS: Use Cocoa implementation of EmacsBell -init if named image is declared

* configure.ac: Check for 'NSImageNameCaution' declaration when
building on GNUstep.
* src/nsterm.m ([EmacsBell init]): Use fallback implementation on
GNUstep only if 'NSImageNameCaution' is not declared.  (Bug#80107)

configure.ac

@@ -2886,6 +2886,11 @@ Mac OS X 12.x or later.
        [Define to use native OS APIs for images.])
      NATIVE_IMAGE_API="yes (ns)"
   fi
+
+  if test "${NS_IMPL_GNUSTEP}" = yes; then
+    AC_CHECK_DECLS([NSImageNameCaution], [], [],
+                   [[#import <AppKit/NSImage.h>]])
+  fi
 fi
 
 AC_SUBST([LIBS_GNUSTEP])

src/nsterm.m

@@ -1221,7 +1221,7 @@ ns_unfocus (struct frame *f)
     {
       nestCount = 0;
       isAttached = false;
-#ifdef NS_IMPL_GNUSTEP
+#if NS_IMPL_GNUSTEP && !HAVE_DECL_NSIMAGENAMECAUTION
       // GNUstep doesn't provide named images.  This was reported in
       // 2011, see https://savannah.gnu.org/bugs/?33396
       //