libxl: add acpi slic table support

Libxl driver did not support setup additional acpi firmware to xen
guest. It is necessary to activate OEM Windows installs. This patch
allow to define in OS section acpi table param (which supported domain
common schema).
Signed-off-by: NIvan Kardykov <kardykov@tabit.pro>
[added info to docs/formatdomain.html.in]
Signed-off-by: NMarek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

docs/formatdomain.html.in

@@ -363,7 +363,8 @@
       <dd>The <code>table</code> element contains a fully-qualified path
         to the ACPI table. The <code>type</code> attribute contains the
         ACPI table type (currently only <code>slic</code> is supported)
-        <span class="since">Since 1.3.5 (QEMU only)</span></dd>
+        <span class="since">Since 1.3.5 (QEMU)</span>
+        <span class="since">Since 5.8.0 (Xen)</span></dd>
     </dl>
 
     <h4><a id="elementsOSContainer">Container boot</a></h4>

src/libxl/libxl_conf.c

@@ -506,6 +506,11 @@ libxlMakeDomBuildInfo(virDomainDefPtr def,
                           def->features[VIR_DOMAIN_FEATURE_ACPI] ==
                           VIR_TRISTATE_SWITCH_ON);
 
+        /* copy SLIC table path to acpi_firmware */
+        if (def->os.slic_table &&
+                VIR_STRDUP(b_info->u.hvm.acpi_firmware, def->os.slic_table) < 0)
+            return -1;
+
         if (def->nsounds > 0) {
             /*
              * Use first sound device.  man xl.cfg(5) describes soundhw as