VMX: Add cdrom-raw dev type from VMWare Fusion

According to VMWare's documentation 'cdrom-raw' is an acceptable value
for deviceType for a CD-ROM drive. The documentation states that the VMX
configuration for a CD-ROM deviceType is as follows:

ide|scsi(n):(n).deviceType = "cdrom-raw|atapi-cdrom|cdrom-image"

From the documentation it appears the following is true:
- cdrom-image = Provides the ISO to the VM
- atapi-cdrom = Provides a NEC emulated ATAPI CD-ROM on top of the host
  CD-ROM
- cdrom-raw = Passthru for a host CD-ROM drive. Allows CD-R burning from
  within the guest.

A CD-ROM prior to this patch would always provide an 'atapi-cdrom' is
modeled as:
  <disk type='block' device='cdrom'>
    <source dev='/dev/scd0'/>
    <target dev='hda' bus='ide'/>
    <address type='drive' controller='0' bus='0' target='0' unit='0'/>
  </disk>

This patch allows the 'device' attribute to be set to 'lun' for a raw
acccess CD-ROM such as:
  <disk type='block' device='lun'>
    <source dev='/dev/scd0'/>
    <target dev='hda' bus='ide'/>
    <address type='drive' controller='0' bus='0' target='0' unit='0'/>
  </disk>

docs/formatdomain.html.in

@@ -1597,8 +1597,7 @@
             defaulting to "disk".
             <p>
             Using "lun" (<span class="since">since 0.9.10</span>) is only
-            valid when type is "block" and the target element's "bus"
-            attribute is "virtio", and behaves identically to "disk",
+            valid when type is "block", and behaves identically to "disk",
             except that generic SCSI commands from the guest are accepted
             and passed through to the physical device. Also note that
             device='lun' will only be recognized for actual raw devices,