move anchor page out of ikiwiki subdir

Since this page is not in the basewiki, it is confusing to put it in
the ikiwiki subdir, which is intended for basewiki and other underlay pages
that are used to document ikiwiki on other wikis.

doc/ikiwiki/wikilink/discussion.mdwn

@@ -1,6 +1,6 @@
-# Creating an [[ikiwiki/anchor]] in Markdown
+# Creating an [[anchor]] in Markdown
 
-Is it a native Markdown "tag" for creating an [[ikiwiki/anchor]]? Unfortunately,
+Is it a native Markdown "tag" for creating an [[anchor]]? Unfortunately,
 I haven't any information about it at
 [Markdown syntax](http://daringfireball.net/projects/markdown/syntax) page.
 

doc/plugins/contrib/headinganchors.mdwn

@@ -1,6 +1,6 @@
 [[!template id=plugin name=headinganchors author="[[PaulWise]]"]]
 
-This is a simple plugin to add ids (which will server as [[ikiwiki/anchor]]s) to all headings, based on their text. It
+This is a simple plugin to add ids (which will serve as [[anchor]]s) to all headings, based on their text. It
 works as a postprocessing filter, allowing it to work on mdwn, wiki, html,
 rst and any other format that produces html. The code is available here: