Added proper structures to implement
glGetActiveUniformsiv and added it to
the Program class.

Change-Id: I41b8fd17b6e533ad2638778de9854206d10fe13d
Reviewed-on: https://swiftshader-review.googlesource.com/3435Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>