layout: remove sizing_eval call when layout is already destructed. @fix

layout: remove sizing_eval call when layout is already destructed. @fix

Summary:
Layout's sub_object_del function calls sizing_eval even if layout's smart_del
function has already been called (Due to widget_smart_del impl).
This patch adds 'destructed_is' flag to Elm_Layout_Smart_Data and prevents unneeded
sizing_eval calls when object is already destructed.
Patch also fixes SIGSEGV in layout derived entry widget caused by calling
sizing_eval after entry_smart_del destructor.

Added entry test to avoid regression for SIGSEGV bug.

Test Plan: run tests/elm_test_entry

Reviewers: raster, seoz, tasn, cedric

Differential Revision: https://phab.enlightenment.org/D823