* configure.in.in: Depend on GTK+ 2.12 and GLib 2.14. Add dependency

	  on GIO 2.14 as well.
	* libxfce4menu/Makefile.am: Add new source and header files.
	* libxfce4menu/libxfce4menu.h: Add new header files.
	* libxfce4menu/xfce-menu-node.{c,h}: Add new class XfceMenuNode which
	  holds the information for one element in the menu DOM tree, e.g.
	  <MergeFile>, <Name> or <Menu>
	* libxfce4menu/xfce-menu-tree-provider.{c,h}: Add new interface
	  XfceMenuTreeProvider for classes which hold a GNode DOM
	  representation for .menu files.
	* libxfce4menu/xfce-menu-parser.{c,h}: Add new parser for .menu XML
	  files. It builds a GNode DOM representation for the XML data. Each
	  GNode in the tree (except for the menu nodes) contains one
	  XfceMenuNode for the XML element information. The parser implements
	  XfceMenuTreeProvider.
	* libxfce4menu/xfce-menu-merger.{c,h}: Add new class XfceMenuMerger
	  which takes the DOM tree from the parser or any other
	  XfceMenuTreeProvider and resolves duplicates, relative paths and,
	  most importantly, merges and deletes menus according to the
	  information in the DOM tree. It implements XfceMenuTreeProvider. It
	  is not complete yet because it doesn't implement <Move> elements
	  and is not capable of consolidating child menus with the same name
	  at the moment.
	* tests/Makefile.am, tests/test-menu-parser.c: Add a small test
	  program which parses a menu file using XfceMenuParser and then runs
	  an XfceMenuMerger and prints the output of both.