- Added new FenceSync object and related
  API functions implementations
- Added FenceSync to ResourceManager
- Moved Sampler to ResourceManager

Change-Id: Ia3d42b749811a4e1ed087b41f0c871beb8fdb8d4
Reviewed-on: https://swiftshader-review.googlesource.com/2931Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>