Use C++11 alignment primitives

Removes the compiler-specific base #define ALIGNOF and replace uses with alignof.

Replaces some uses of ALIGNAS with alignas. These are not all replaced,
and a note is added to the definition about the problems with alignas.
This came from https://codereview.chromium.org/2670873002/

Remove base::AlignedMemory and replace with alignas(type) char[size].

std::aligned_storage has some limitations. The style guide is updated to note these and mark it disallowed. It is also updated for alignas and alignof.

CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2932053002
Cr-Commit-Position: refs/heads/master@{#479169}
31 files changed