QemuOpts: add -set option

One use case will be file for drives (no filename quoting issues), i.e.

	-drive id=test,if=virtio
	-set drive.test.file=/vmdisk/test-virtio.img

It will work for any other option (assuming handled by QemuOpts) though.
Except for id= for obvious reasons ;).

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Message-Id: 
diff --git a/vl.c b/vl.c
index ca84fa9..5542df3 100644
--- a/vl.c
+++ b/vl.c
@@ -4966,6 +4966,10 @@
             case QEMU_OPTION_drive:
                 drive_add(NULL, "%s", optarg);
 	        break;
+            case QEMU_OPTION_set:
+                if (qemu_set_option(optarg) != 0)
+                    exit(1);
+	        break;
             case QEMU_OPTION_mtdblock:
                 drive_add(optarg, MTD_ALIAS);
                 break;