[SPARK-6855] [SPARKR] Set R includes to get the right collate order.

This prevents tools like devtools::document creating invalid collate orders

Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #5462 from shivaram/collate-order and squashes the following commits:

f3db562 [Shivaram Venkataraman] Set R includes to get the right collate order. This prevents tools like devtools::document creating invalid collate orders