doxygen: provide a more meaningful order for results.

doxygen: provide a more meaningful order for results.

Results of the same length are now ordered like this, instead of
appearing in whatever order they were added:

 * Deprecated and deleted symbols are put on the bottom
 * Then ordered by type:
   * First pages, since they usually provide most information
   * Then namespaces and groups
   * Then classes, structs, unions
   * Then functions
   * Then macros
   * Then enums
   * And enum values and variables last
 * After that, items with the shorter suffix (the least amount of
   function arguments) are preferred over longer
 * Finally, items with shorter prefix are preferred over longer (so e.g.
   it shows a Foo in the root namespace over Foo which is 5 levels deep)

This might get fine-tuned later, but I'm already very happy with the
result.