[coretext] Fix drawing fallback fonts
[coretext] Fix drawing fallback fonts

Core Text will apply its font fallback mechanism when typesetting a
CTLine, and we can't assume that the returned run all use the original
font. This fixes the random glyphs drawn when we hit font fallback.

Change-Id: Id4d7098cb7bd3464cba6abab22be3ac3942c8889
Reviewed-on: https://gerrit.libreoffice.org/3846
Reviewed-by: Tor Lillqvist <a9ff1a38c0d094d92725714af3aa7948469a0905@iki.fi>
Tested-by: Tor Lillqvist <a9ff1a38c0d094d92725714af3aa7948469a0905@iki.fi>

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core