[bootstrap/win] Upgrade Python to 2.7.13.

Upgrade Python on Windows to 2.7.13, and use 64-bit Python on 64-bit
Windows systems.

BUG=chromium:741001
TEST=local

Change-Id: Ib30ccec580a0db8ee59be3f027f96b039b0097fe
Reviewed-on: https://chromium-review.googlesource.com/571171Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Daniel Jacques <dnj@chromium.org>

bootstrap/win/manifest_bleeding_edge.txt

@@ -12,7 +12,7 @@
 # to extract VERSION.
 
 @Subdir python
-infra/python/cpython/windows-386 version:2.7.6
+infra/python/cpython/${platform} version:2.7.13.chromium7
 
 @Subdir git
 infra/git/${platform} version:2.10.0