Support wtz-foreign protocol

Support wtz-foreign protocol

This is an initial commit to support wtz-foreign protocol.

This is to support out-of-process video playing surface.
wtz-foreign protocol is to enable one client to share its resources to
another client.
The client which exported a reference of foreign shell then can change
attributes - such as size, orientation, and map state - of foreign shell.
So, the client which import a foreign shell can draw its contents onto a
surface without concerning about attributes such as size like as
mentioned.

The e_foreign contains implementation of wtz_exporter and wtz_importer.
And e_foreign_shell contains implementation of wtz_exported_shell and
wtz_foreign_shell.

Change-Id: Idec6194d9b57e3346167eaa4ab6537b4d59c3393