We previously had UNIFORM_BUFFER_OFFSET_ALIGNMENT set to 1. That
value was arbitrary, and WebGL expects that value to be 4, so I
made the change.

Fixes WebGL 2 test:
deqp/functional/gles3/negativebufferapi.html

Change-Id: I7ab654cce629ac2a5dffc9a9d3bff3c1fb1ec8c7
Reviewed-on: https://swiftshader-review.googlesource.com/16608Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>