Loaddenver612

Update to VS2013 Update 4, and Windows SDK 8.1- Disable 4996 (deprecated functions in 8.1, these don't help us because we have to run on old OSs anyway)- Simplify Bluetooth LE header hacks (these headers are buggy in 8.0 and 8.1 SDKs, but less buggy in 8.1)- Revert attempt to centralize toolchain hashes as it didn't work well, and made it hard to roll anyway (see 400830).- Instead of basing C4702 (unreachable code) on Pro vs. Express, check whether it's actually disabled in the xtree header- Remove automatic calling of Express toolchain setup script. It hasn't worked well since post VS2013 RTM because of being distributed as .msp files, and the new Community edition is relatively easy to install so can subsume that usage (that being the motivation for the 4702 change above)- goma package for u4 is pushed- ANGLE is switched to load d3dcompiler_47 and build against 8.1 sdk, roll included here.Xrefs:- https://codereview.chromium.org/719343004/- https://chromium-review.googlesource.com/#/c/229616/- b2/18365241- https://codereview.chromium.org/733563003/- https://codereview.chromium.org/732673002/- https://codereview.chromium.org/729453004/- https://chromereviews.googleplex.com/120597013/BUG=311488, 432748, 400830Committed: https://crrev.com/a6675a5f1f55e66b1d6625af6225d44f5d9b0f3dCr-Commit-Position: refs/heads/master@{#304329}