Add support for 32-bit framebuffers.

This modifies the emulator so support 32-bit framebuffers.
You can create such a frame-buffer using one of these methods:

- Add a "bpp 32" line to the "display" element of your skin
- Use the new 'magic' skin option format: e.g. -skin 320x480x32

Note that the result will be hideous since the kernel driver still
thinks the hardware is only 16-bits. This will be addressed in a
later patch to hw/goldfish_fb.c and to the kernel driver
($KERNEL/drivers/video/goldfishfb.c)

Change-Id: I0fc700c4a4cb8521076605324e15ed34e5d01136
diff --git a/android/display.c b/android/display.c
index d7c261a..8bad585 100644
--- a/android/display.c
+++ b/android/display.c
@@ -88,7 +88,7 @@
     ds->opaque    = qf;
     ds->surface   = qemu_create_displaysurface_from(qf->width,
                                                     qf->height,
-                                                    16,
+                                                    qf->bits_per_pixel,
                                                     qf->pitch,
                                                     qf->pixels);