[Mac] Disable screen font substitution at WebCore-level in OS X 10.9+
<http://webkit.org/b/119474>
<rdar://problem/14643349>

Reviewed by Dan Bernstein.

Disable screen font substitution by default in Settings so internal WebCore clients
such as SVG-as-image will get the right default setting.

* page/Settings.cpp:
(WebCore::Settings::Settings):
(WebCore::Settings::shouldEnableScreenFontSubstitutionByDefault):
(WebCore::Settings::setScreenFontSubstitutionEnabled):
* page/Settings.h:
(WebCore::Settings::screenFontSubstitutionEnabled):
* page/Settings.in:
* page/mac/SettingsMac.mm:
(WebCore::Settings::shouldEnableScreenFontSubstitutionByDefault):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@153696 268f45cc-cd09-0410-ab3c-d52691b4dbfc