Fix doc-related glitches in Makefile and .gitignore

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

Makefile

@@ -165,7 +165,7 @@ clean: clean-doc
 	rm -f cgit VERSION *.o *.d
 
 clean-doc:
-	rm -f cgitrc.5 cgitrc.5.xhtml cgitrc.5.pdf
+	rm -f cgitrc.5 cgitrc.5.html cgitrc.5.pdf cgitrc.5.xml cgitrc.5.fo
 
 get-git:
 	curl $(GIT_URL) | tar -xj && rm -rf git && mv git-$(GIT_VER) git