Mark generated @yields on classes and rate-each as such on symbols

* src/current/include/preproc/expand.xsl
  (lv:classify): Set `@preproc:yields-generated' if `@yields' was not
    previously defined.
* src/current/include/preproc/macros.xsl:
  (lv:rate-each): Set `@preproc:yields-generated` if `@yields' was not
    previously defined.
* src/current/include/preproc/symtable.xsl:
  (lv:rate, lv:classify): Set `@preproc:generated` on symbol if
    `@preproc:yields-generated'.

src/current/include/preproc/expand.xsl

@@ -550,6 +550,9 @@
         <!-- certain characters are not valid for @yields -->
         <xsl:value-of select="translate( @as, '-', '' )" />
       </xsl:attribute>
+
+      <xsl:attribute name="preproc:yields-generated"
+                     select="'true'" />
     </xsl:if>
 
     <xsl:apply-templates mode="preproc:expand"

src/current/include/preproc/macros.xsl

@@ -406,6 +406,8 @@
         <xsl:otherwise>
           <xsl:attribute name="yields"
                          select="concat( '_', @generates )" />
+          <xsl:attribute name="preproc:yields-generated"
+                         select="'true'" />
         </xsl:otherwise>
       </xsl:choose>
     </xsl:if>

src/current/include/preproc/symtable.xsl

@@ -660,7 +660,12 @@
 
   <preproc:sym name="{@yields}" type="rate"
     extclass="{$external}"
-    local="{@local}" dtype="float" dim="0" tex="{@sym}" />
+    local="{@local}" dtype="float" dim="0" tex="{@sym}">
+
+    <xsl:if test="@preproc:yields-generated">
+      <xsl:attribute name="preproc:generated" select="'true'" />
+    </xsl:if>
+  </preproc:sym>
 
   <xsl:apply-templates mode="preproc:symtable" />
 </xsl:template>
@@ -736,6 +741,10 @@
       extclass="{$external}" terminate="{$terminate}"
       type="cgen" dtype="boolean" dim="?" desc="{@desc}">
 
+      <xsl:if test="@preproc:yields-generated">
+        <xsl:attribute name="preproc:generated" select="'true'" />
+      </xsl:if>
+
       <xsl:sequence select="@preproc:*" />
     </preproc:sym>
   </xsl:if>