Remove GCC 4.6 support

Remove GCC 4.6 support

All our supported platforms have GCC 4.8 or higher available.
That includes Tizen TV 2.2.1, 2.4 and 3.0, as well as Tizen
Mobile 2.4 and 3.0.
The last known Tizen platform that depends on GCC 4.6 is
Tizen 2.3, which is not supported by the current dev and
beta branches.

Additionally, since the m42 upversion and the Xwalk refactor
work switched over to m42, GCC 4.6 specific hacks were not
carried over to s-chromium and s-blink. So the code being
removed is non-functional anymore anyways.

The only file left over is gcc46_compat_wrappers/ecore_x_wrapper.h
which will be used to support wayland. I deliberately
left this file over to avoid merge conflicts with that work.

Bug: http://107.108.218.239/bugzilla/show_bug.cgi?id=12987
Reviewed by: Piotr Tworek, SeungSeop Park

Change-Id: Id3cd6ecff1a41a40f300d70d67e7b14bf7ac37ab
Signed-off-by: Antonio Gomes <a1.gomes@samsung.com>