Typo and comment fixes

* docs/schemas/*.rng: the comments were wrong
* src/qemu_conf.c: typo in an error message

docs/schemas/capability.rng

-<!-- A Relax NG schema for the libvirt node device XML format -->
+<!-- A Relax NG schema for the libvirt capabilities XML format -->
 <grammar xmlns="http://relaxng.org/ns/structure/1.0"
     datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
-  <!-- We handle only document defining a domain -->
   <start>
     <ref name='capabilities'/>
   </start>

docs/schemas/nodedev.rng

 <!-- A Relax NG schema for the libvirt node device XML format -->
 <grammar xmlns="http://relaxng.org/ns/structure/1.0"
     datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
-  <!-- We handle only document defining a domain -->
   <start>
     <ref name='device'/>
   </start>
 
-  <!--
-      We handle only document defining a domain
-    -->
   <define name='device'>
     <element name="device">
       <!-- The name of the network, used to refer to it through the API

docs/schemas/storagepool.rng

-<!-- A Relax NG schema for the libvirt node device XML format -->
+<!-- A Relax NG schema for the libvirt storage pool XML format -->
 <grammar xmlns="http://relaxng.org/ns/structure/1.0"
     datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
-  <!-- We handle only document defining a domain -->
   <start>
     <ref name='pool'/>
   </start>

docs/schemas/storagevol.rng

-<!-- A Relax NG schema for the libvirt node device XML format -->
+<!-- A Relax NG schema for the libvirt storage volume XML format -->
 <grammar xmlns="http://relaxng.org/ns/structure/1.0"
     datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
-  <!-- We handle only document defining a domain -->
   <start>
     <ref name='vol'/>
   </start>

src/qemu_conf.c

@@ -1970,7 +1970,7 @@ int qemudBuildCommandLine(virConnectPtr conn,
     if (def->nvideos) {
         if (def->nvideos > 1) {
             qemudReportError(conn, NULL, NULL, VIR_ERR_INTERNAL_ERROR,
-                             "%s", _("only one video card is currentely supported"));
+                             "%s", _("only one video card is currently supported"));
             goto error;
         }