Uniform blocks implementation

- Added support for uniform blocks in OutputASM::declareUniform
- Added basic implementation of Program::applyUniformBuffers()
  to be completed later on when uniform buffers are implemented

Change-Id: I919b59d4557bb10bb302e6b6bd0ada79553ca8bb
Reviewed-on: https://swiftshader-review.googlesource.com/3651
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>