devel/R-cran-bigmemory.sri: New port

bigmemory.sri provides a shared resource interface for the bigmemory
and synchronicity packages in R.

Approved by: fuz (mentor), imp (previous revision), mat (previous revision)
Reviewed by: fuz (mentor), imp (previous revision), mat (previous revision)
Differential Revision: https://reviews.freebsd.org/D22676