Implemented the necessary functions
for the API level implementation of
glBindBufferBase and glBindBufferRange.
Also cleaned up the TransformFeedback
API functions a little for uniformity
with uniform buffers.

Change-Id: Iccc835f175d4e8bc4ee030343936714b7ff224ac
Reviewed-on: https://swiftshader-review.googlesource.com/3030Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>