[WIN32K] CreateDIBPalette addendum to #3758 CORE-17626

Fix compilation on older GCC4.7.2 toolchain
to not warn about universal zero initializer.
See
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53119
https://stackoverflow.com/questions/13746033/how-to-repair-warning-missing-braces-around-initializer

win32ss/gdi/ntgdi/dibobj.c

@@ -127,7 +127,7 @@ CreateDIBPalette(
         {
             /* The colors are an array of RGBQUAD values */
             RGBQUAD *prgb = (RGBQUAD*)((PCHAR)pbmi + pbmi->bmiHeader.biSize);
-            RGBQUAD colors[256] = {0};
+            RGBQUAD colors[256] = {{0}};
 
             // FIXME: do we need to handle PALETTEINDEX / PALETTERGB macro?