evas: Support bitmap embedded color font.

evas: Support bitmap embedded color font.

Summary:
Add the code for getting bitmap buffers from embedded color font,
And draw the bitmap buffers as images.
For drawing the bitmap buffers as images,
evas_common_draw_context_font_ext_set internal API is changed to
pass additional gl engine functions.
T2139
@feature

Test Plan:
1. Set a bitmap embedded color font to textblock.
2. Set a unicode emoticon text.
3. See the result.

Please check the sample unicode in the following link.
http://www.fileformat.info/info/unicode/char/1f3af/index.htm
http://www.fileformat.info/info/unicode/char/1f555/index.htm
http://www.fileformat.info/info/unicode/char/2600/index.htm
http://www.fileformat.info/info/unicode/char/263a/index.htm

Reviewers: tasn, woohyun, jpeg, raster

Reviewed By: raster

Subscribers: herdsman, cedric

Differential Revision: https://phab.enlightenment.org/D2084