Require 16-byte alignment for Vulkan objects
Require 16-byte alignment for Vulkan objects

At least for large formats, we assume 16 byte alignment for render
target writes. Requiring 16 bytes in general seems a good idea for
x86_64.

Bug: b/127721996
Change-Id: Ie4d2d9bf71fb8a3d8b58f099785e75a72ff0e181
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/26448
Tested-by: Chris Forbes <c3279c50043e18e9442c1ae071cafa0e7a4ca967@google.com>
Presubmit-Ready: Chris Forbes <c3279c50043e18e9442c1ae071cafa0e7a4ca967@google.com>
Reviewed-by: Ben Clayton <1f693eb7158dc33015048c09d6712f74dabddf79@google.com>
Reviewed-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>
Reviewed-by: Alexis Hétu <1c7141772178a7e80858c3db5052b328076f08f4@google.com>
Kokoro-Presubmit: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,bkaradzic/SwiftShader