Move Windows safe file creation code into WebCore from WebPreferences

 Move Windows safe file creation code into WebCore from WebPreferences

 WebCore:

         Move Windows safe file creation code into WebCore from WebPreferences

         Reviewed by Brady.

         * platform/FileSystem.h:
         * platform/win/FileSystemWin.cpp:
         (WebCore::safeCreateFile): Moved here from WebKit/win/WebPreferences.cpp.

 WebKit/win:

         Move safe file creation code to WebCore

         Reviewed by Brady.

         * WebPreferences.cpp:
         (preferencesPath): Made into a static helper function.
         (WebPreferences::save): Now calls WebCore's safeCreateFile function.
         (WebPreferences::load): Uses String/CString to handle the UTF-8
         conversion.
         * WebPreferences.h: Removed preferencesPath and
         safeCreateFileWithData.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@26991 268f45cc-cd09-0410-ab3c-d52691b4dbfc