symtable: Speed up processing a bit

This uses the same map strategy (and same duplicate code) as previous
commits, but this one generates a map for two separate tables.

There is more room for improvement, but this cuts down on the time a
lot.  Also keep in mind that this is performed multiple times (once per
pass), so it's still worth revisiting.  Performance is still very poor for
very large (many thousands of symbols) symbol tables.

The next slowest part appears to be the fragment compilation.  I'm nearing
the end of the low-low-hanging fruit for maps.  The /common/gl package
mentioned in previous commits that previously took over a minute to compile
now compiles in 20s as of this commit on equivalent hardware.

* src/current/include/preproc/symtable.xsl (@xmlns:map): New namespace
    declaration.
  (preproc:symtable-process-symbols): Create map for `cursym' and
    `extresults'.  Use it.  Remove unused `dup'.  Output message when
    done (another is output slightly later on in the process).

src/current/include/preproc/symtable.xsl

@@ -62,6 +62,7 @@
 <stylesheet version="2.0"
             xmlns="http://www.w3.org/1999/XSL/Transform"
             xmlns:xs="http://www.w3.org/2001/XMLSchema"
+            xmlns:map="http://www.w3.org/2005/xpath-functions/map"
             xmlns:symtable="http://www.lovullo.com/tame/symtable"
             xmlns:preproc="http://www.lovullo.com/rater/preproc"
             xmlns:lv="http://www.lovullo.com/rater"
@@ -438,37 +439,35 @@
   <param name="new"        as="element( preproc:syms )" />
   <param name="this-pkg"   as="element( lv:package )" />
 
+  <message>
+    <text>[preproc/symtable] processing symbol table...</text>
+  </message>
+
+  <variable name="cursym" as="element( preproc:sym )*"
+                select="preproc:symtable/preproc:sym[
+                          not( @held = 'true' ) ]" />
+
+  <variable name="cursym-map" as="map( xs:string, element( preproc:sym ) )"
+            select="map:merge(
+                      for $sym in $cursym
+                        return map{ string( $sym/@name ) : $sym } )" />
+
+  <variable name="extresults-map" as="map( xs:string, element( preproc:sym ) )"
+            select="map:merge(
+                      for $sym in $extresults/preproc:sym
+                        return map{ string( $sym/@name ) : $sym } )" />
+
   <preproc:syms>
-    <variable name="cursym" as="element( preproc:sym )*"
-                  select="preproc:symtable/preproc:sym[
-                            not( @held = 'true' ) ]" />
-
     <sequence select="$cursym" />
 
-    <message>
-      <text>[preproc/symtable] processing symbol table...</text>
-    </message>
-
     <for-each select="$new/preproc:sym[ not( @extern='true' and @src ) ]">
       <variable name="name" select="@name" />
       <variable name="src" select="@src" />
-      <variable name="dupall" select="
-          (
-            preceding-sibling::preproc:sym,
-            $cursym,
-            $extresults/preproc:sym
-          )[
-            @name=$name
-          ]
-        " />
-      <variable name="dup" select="
-          $dupall[
-            not(
-              @src=$src
-              or ( not( @src ) and not( $src ) )
-            )
-          ]
-        " />
+
+      <variable name="dupall" as="element( preproc:sym )*"
+                select="$cursym-map( $name ),
+                        $extresults-map( $name ),
+                        preceding-sibling::preproc:sym[ @name = $name ]" />
 
       <choose>
         <when test="@pollute='true' and not( @type )">
@@ -509,6 +508,8 @@
       </choose>
     </for-each>
   </preproc:syms>
+
+  <message select="'[preproc/symtable] done processing symbol table.'" />
 </template>