Fix missing std.logger.core module in the navigation tree.

The default version of "lookup" will lookup a symbol in ancestor scopes if it isn't found within the main scope, matching the "core." top level package in this particular case.

Author: s-ludwig

dpl-docs/views/ddox.inc.module-tree.dt

@@ -17,7 +17,7 @@
 				span Package members
 
 	- foreach(m; pack.modules)
-		- if (pack.lookup!Package(m.name))
+		- if (pack.lookup!Package(m.name, false))
 			- continue;
 		li
 			a.module(href="#{info.linkTo(m)}", class='#{info.node is m || m.isAncestorOf(info.node) ? "selected" : ""}')