Fix problem that press CTRL+ALT+2 and then CTRL+ALT+1 back to VM graphic console, screen cannot be restored. 
xenfb_guest_copy only handles xenfb->depth=8 and 24 cases, because it assumes in xenfb->depth=16 or 32 cases,
buffer is shared, like in xenfb_update ==> qemu_create_displaysurface_from() does. But as the mentioned bug,
it didn't enter the xenfb_update do_resize hunk, buffer is not shared.
To solve that problem, either make it enter the xenfb_update do_resize hunk, or change xenfb_guest_copy(), let
it handle all cases. This patch is to let xenfb_guest_copy handle xenfb->depth=32 case.

diff -r e4f337bb97f7 tools/ioemu-qemu-xen/hw/xenfb.c
--- a/tools/ioemu-qemu-xen/hw/xenfb.c	Wed Oct 20 19:39:28 2010 +0800
+++ b/tools/ioemu-qemu-xen/hw/xenfb.c	Wed Oct 20 21:42:37 2010 +0800
@@ -612,6 +612,12 @@
     uint8_t *data = ds_get_data(xenfb->c.ds);
 
     if (!is_buffer_shared(xenfb->c.ds->surface)) {
+        if (xenfb->depth == bpp) { 
+                for (line = y; line < (y+h); line++) {
+                        memcpy (data + (line * linesize) + (x * bpp / 8), xenfb->pixels + xenfb->offset + (line * xenfb->row_stride) + (x * xenfb->depth / 8), w * xenfb->depth / 8);
+                }
+        }
+        else{
         switch (xenfb->depth) {
         case 8:
             if (bpp == 16) {
@@ -631,9 +637,17 @@
                 oops = 1;
             }
             break;
+        case 32:
+            if (bpp == 16) {
+                BLT(uint32_t, uint16_t,  8, 8, 8,   5, 6, 5);
+            } else {
+                oops = 1;
+            }
+            break; 
         default:
             oops = 1;
 	}
+        }
     }
     if (oops) /* should not happen */
         xen_be_printf(&xenfb->c.xendev, 0, "%s: oops: convert %d -> %d bpp?\n",