Introduce a new type="dir" mode for <disks> that allows use of
QEMU's virtual FAT block device driver. eg
<disk type='dir' device='floppy'>
<source dir='/tmp/test'/>
<target dev='fda' bus='fdc'/>
<readonly/>
</disk>
gets turned into
-drive file=fat:floppy:/tmp/test,if=floppy,index=0
Only read-only disks are supported with virtual FAT mode
* src/conf/domain_conf.c, src/conf/domain_conf.h: Add type="dir"
* docs/schemas/domain.rng: Document new disk type
* src/xen/xend_internal.c, src/xen/xm_internal.c: Raise error for
unsupported disk types
* tests/qemuxml2argvdata/qemuxml2argv-disk-cdrom-empty.args: Fix
empty disk file handling
* tests/qemuxml2argvdata/qemuxml2argv-disk-drive-fat.args,
tests/qemuxml2argvdata/qemuxml2argv-disk-drive-fat.xml,
tests/qemuxml2argvdata/qemuxml2argv-floppy-drive-fat.args,
tests/qemuxml2argvdata/qemuxml2argv-floppy-drive-fat.xml
tests/qemuxml2argvtest.c: Test QEMU vitual FAT driver
* src/qemu/qemu_conf.c: Support generating fat:/some/dir type
disk args
* src/security/security_selinux.c: Temporarily skip labelling
of directory based disks
