pgsql: New C function: bms_add_range

New C function: bms_add_range

This will be used by pending patches to improve partition pruning.

Amit Langote and Kyotaro Horiguchi, per a suggestion from David
Rowley.  Review and testing of the larger patch set of which this is a
part by Ashutosh Bapat, David Rowley, Dilip Kumar, Jesper Pedersen,
Rajkumar Raghuwanshi, Beena Emerson, Amul Sul, and Kyotaro Horiguchi.

Discussion: http://postgr.es/m/098b9c71-1915-1a2a-8d52-1a7a50ce79e8@lab.ntt.co.jp

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/84940644de931f331433b35e3a391822671f8c9c

Modified Files
--------------
src/backend/nodes/bitmapset.c | 72 +++++++++++++++++++++++++++++++++++++++++++
src/include/nodes/bitmapset.h |  1 +
2 files changed, 73 insertions(+)