move list of namespaces to its own section

doc/tips/convert_mediawiki_to_ikiwiki.mdwn

@@ -48,10 +48,7 @@ in HTML, you may need to add further processing to the last line.
 
 Note that by default, `Special:Allpages` will only list pages in the main
 namespace. You need to add a `&namespace=XX` argument to get pages in a
-different namespace. The following numbers correspond to common namespaces:
-
- * 10 - templates (`Template:foo`)
- * 14 - categories (`Category:bar`)
+different namespace. (See below for the default list of namespaces)
 
 Note that the page names obtained this way will not include any namespace
 specific prefix: e.g. `Category:` will be stripped off.
@@ -67,6 +64,12 @@ MySQL backend, the page table is, appropriately enough, called `table`:
 As with the previous method, you will need to do some filtering based on the
 namespace.
 
+### namespaces
+
+The list of default namespaces in mediawiki is available from <http://www.mediawiki.org/wiki/Manual:Namespace#Built-in_namespaces>, reproduced here for convenience:
+
+[[mediawiki_namespaces]]
+
 ## Step 2: fetching the page data
 
 Once you have a list of page names, you can fetch the data for each page.