Remove references to non-chromium entries from WebCore.gypi (part 2)
https://bugs.webkit.org/show_bug.cgi?id=103124

Reviewed by Pavel Feldman.

* WebCore.gypi: removed unused references to gtk, cf, win and mac

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146874 268f45cc-cd09-0410-ab3c-d52691b4dbfc