set commented-out code to 1

so it can be uncommented to enable

doc/ikiwiki.setup

@@ -131,7 +131,7 @@ use IkiWiki::Setup::Standard {
 	#recentchangespage => "recentchanges",
 	#recentchangesnum => 100,
 	# Use new '!'-prefixed preprocessor directive syntax
-	#prefix_directives => 0,
+	#prefix_directives => 1,
 	# Attempt to make hardlinks to source files instead of copying them.
 	# Useful if the wiki contains large media files.
 	#hardlink => 1,