windowscodecs: Autoconf macros don't always have a value.

dlls/windowscodecs/pngformat.c

@@ -176,7 +176,7 @@ MAKE_FUNCPTR(png_get_tRNS);
 MAKE_FUNCPTR(png_set_bgr);
 MAKE_FUNCPTR(png_set_crc_action);
 MAKE_FUNCPTR(png_set_error_fn);
-#if HAVE_PNG_SET_EXPAND_GRAY_1_2_4_TO_8
+#ifdef HAVE_PNG_SET_EXPAND_GRAY_1_2_4_TO_8
 MAKE_FUNCPTR(png_set_expand_gray_1_2_4_to_8);
 #else
 MAKE_FUNCPTR(png_set_gray_1_2_4_to_8);
@@ -225,7 +225,7 @@ static void *load_libpng(void)
         LOAD_FUNCPTR(png_set_bgr);
         LOAD_FUNCPTR(png_set_crc_action);
         LOAD_FUNCPTR(png_set_error_fn);
-#if HAVE_PNG_SET_EXPAND_GRAY_1_2_4_TO_8
+#ifdef HAVE_PNG_SET_EXPAND_GRAY_1_2_4_TO_8
         LOAD_FUNCPTR(png_set_expand_gray_1_2_4_to_8);
 #else
         LOAD_FUNCPTR(png_set_gray_1_2_4_to_8);
@@ -467,7 +467,7 @@ static HRESULT WINAPI PngDecoder_Initialize(IWICBitmapDecoder *iface, IStream *p
         {
             if (bit_depth < 8)
             {
-#if HAVE_PNG_SET_EXPAND_GRAY_1_2_4_TO_8
+#ifdef HAVE_PNG_SET_EXPAND_GRAY_1_2_4_TO_8
                 ppng_set_expand_gray_1_2_4_to_8(This->png_ptr);
 #else
                 ppng_set_gray_1_2_4_to_8(This->png_ptr);