Enable VS2013 for Windows compilation by default.
Enable VS2013 for Windows compilation by default.

BUG=chromium:340973
TEST=All trybots passing runhooks and compile step (needs clobber flag -c to ensure old compile output doesn't cause it to fail). I also ran all the tests for the Windows trybots, which passed.
R=tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/9769004

Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: c2313fb73cc0211b2bae9a0e01f7e095b21ddb6e

sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc