Put the nselib/* loader at the front, not the end, of the loaders list.

The loaders list determines the order in which places are checked for
Lua modules. I had a problem on Windows when the nmap.exe directory
contained WinPcap's packet.dll. There was a runtime error when liblua
tried to open packet.dll instead of our packet.lua. This way we check
for our own files first.

nse_main.lua

@@ -128,7 +128,7 @@ do -- Add loader to look in nselib/?.lua (nselib/ can be in multiple places)
       return "\n\tNSE failed to find "..name.." in search paths.";
     end
   end
-  insert(package.loaders, loader);
+  insert(package.loaders, 1, loader);
 end
 
 local script_database_type, script_database_path =