Extend disabling of whole-program-optimizations to MSVC 2012 https://bugs.webkit.org/show_bug.cgi?id=119238

Reviewed by Jocelyn Turcotte.

As suggested in https://bugreports.qt-project.org/browse/QTBUG-20556,
the WebKit build with MSVC 2012 is affected by the same size
limitations.

* WebCore.pri:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@153464 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Change-Id: I586a600a4a7b18db01ec708466fbf8c6ffe215eb
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>