[Elm_Dnd] Fix type matching of drag and drop target objects in X11.

[Elm_Dnd] Fix type matching of drag and drop target objects in X11.

Summary:
Type matching for drag and drop targets does not consider drop target objects' types.

For example, we have drag object which provides image type and drop target object which only accepts text type.
For current code, in _x11_dnd_drop function, we only check savedtypes.types with _x11_atoms.
As result, we allows the image to be dropped into text. You can refer to the test in D617.

This path fixes this issue by matching drag object's type with drop targets' types to find suitable one.
@fix

Reviewers: raster, JackDanielZ, seoz, woohyun

Differential Revision: https://phab.enlightenment.org/D628