Remove math/libR
- The libR option in math/R has been turned on by default since 2016-06-26.
- A request for comments regarding the removal, posted to ports@ on 2016-07-16, did not result in any requests for it to remain in the tree.
- After a restructuring of math/R, math/libR has been marked BROKEN since 2016-07-09 without any complaints.
- No ports depend on it.
Approved by: swills (mentor)
Differential Revision: https://reviews.freebsd.org/D8260