Preprocess input map nodes

In particular, I want it to handle absolute import paths.  It does
this for the return map; I forgot to add it here.

* src/current/compiler/map.xsl (lvmc:compile) [lvm:program-map]:
  Preprocess nodes.

src/current/compiler/map.xsl

@@ -104,8 +104,8 @@
         <with-param name="type-prefix" select="'map'" />
       </call-template>
 
-      <!-- copy all source nodes -->
-      <sequence select="node()" />
+      <!-- copy source nodes -->
+      <apply-templates mode="preproc:expand" select="node()" />
     </lv:package>
   </variable>