sdl.c: support 32 bpp cursors

Hello,
currently when a 32 bpp cursor gets defined the result is all-black in
the areas that are not transparent (you'll get a 32 bpp cursor if you
use my previous patch to allow vmware_vga to use a 32 bpp framebuffer).
This is because the switch in sdl.c lacks a 32 bpp case.
The thing I am unsure about though is which byte is the unused one and
should be skipped, the first or the last - for the black-and-white
cursors I tested it doesn't make a difference...
Signed-off-by: NReimar Döffinger <Reimar.Doeffinger@gmx.de>
Signed-off-by: NAndrzej Zaborowski <balrogg@gmail.com>

sdl.c

@@ -771,6 +771,9 @@ static void sdl_mouse_define(int width, int height, int bpp,
         line = image;
         for (x = 0; x < width; x ++, dst ++) {
             switch (bpp) {
+            case 32:
+                src = *(line ++); src |= *(line ++); src |= *(line ++); line++;
+                break;
             case 24:
                 src = *(line ++); src |= *(line ++); src |= *(line ++);
                 break;