Fix gen-special when an entity is commented out:

In the xorg application, mkfontdir is commented out, but we did not
check that because it was complicated with the shell. This was
leading to mkfontfir appearing in the packages to install, which
is not wanted. We use the information in the "cat" command to
eliminate the commented out package.

BLFS/gen-special.sh

@@ -133,7 +133,11 @@ EOF
       if [ "$i" = "$packname" ]; then break; fi
       precpack=$i
     done
-
+# It may happen that packname is not in list_cat, because its entity
+# is commented out in the xml, but we do not check that (too complicated).
+# In that case, the whole list is scanned, and $precpack=$i at the end.
+# when packname is found in the list $precpack!=$i.
+    if [ "$precpack" = "$i" ]; then continue; fi
     cat >>$SPECIAL_FILE << EOF
         <module><xsl:text>&#xA;          </xsl:text>
           <xsl:element name="name">$packname</xsl:element>