Disable warning 4702 which affects map, xlist and others on vs2012 and vs2013.
BUG=3584
TESTED=python webrtc\build\gyp_webrtc -G msvs_version=2013 & ninja -C out\Release
R=pthatcher@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/13089004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6801 4adac7df-926f-26a2-2b94-8c16560cd09d