Fix TIVI-2498:"ecore_wayland:didn't set opaque region properl"

Fix TIVI-2498:"ecore_wayland:didn't set opaque region properl"

more info in jira:
   https://bugs.tizen.org/jira/browse/TIVI-2498

This patch basically come from 2 upstream commits
"67769cc39fed35080fe8c145ba7a9635124f77b9
ecore-wayland: Improve opaque setting logic." and
"7a7a0b829734a9f649ebf6e1511381b1dda6a32d ecore/wayland:
Add ecore_wl_window_alpha_set()." plus some tiny fixes.

Without the second commit, there will be black bar issue
if surface uses alpha channel. See
"https://review.tizen.org/gerrit/gitweb?p=platform/upstream/ecore.git;
a=commit;h=d2579e0e3399339d5f47223edcb8e0d485b8749a"
for details about this issue.

Signed-off-by: Li,Limin <liminx.li@intel.com>
Change-Id: Ibdb9f68697855545c995be1877f1d117d18a8a1a