doc: clean up makefile

The sectn and ulink hacks are not necessary since pandoc has been defaulting to Docbook 5 for a long time.
With the pandoc patches, we can get rid of id→xml:id replacement and xmlns hacks as well.

doc/Makefile

@@ -87,24 +87,12 @@ functions/library/generated: doc-support/result
 	ln -rfs ./doc-support/result/function-docs functions/library/generated
 
 %.section.xml: %.section.md
-	pandoc $^ -w docbook \
+	pandoc $^ -t docbook \
 		-f markdown+smart \
-	  | sed -e 's|<ulink url=|<link xlink:href=|' \
-	      -e 's|</ulink>|</link>|' \
-	      -e 's|<sect. id=|<section xml:id=|' \
-	      -e 's|</sect[0-9]>|</section>|' \
-	      -e '1s| id=| xml:id=|' \
-	      -e '1s|\(<[^ ]* \)|\1xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" |' \
 	| cat  > $@
 
 %.chapter.xml: %.chapter.md
-	pandoc $^ -w docbook \
+	pandoc $^ -t docbook \
 		--top-level-division=chapter \
 		-f markdown+smart \
-	  | sed -e 's|<ulink url=|<link xlink:href=|' \
-	      -e 's|</ulink>|</link>|' \
-	      -e 's|<sect. id=|<section xml:id=|' \
-	      -e 's|</sect[0-9]>|</section>|' \
-	      -e '1s| id=| xml:id=|' \
-	      -e '1s|\(<[^ ]* \)|\1|' \
 	| cat  > $@