postgresql-postgis2: Update to 3.1.0

packaging changes:  PostgresQL 9.5 is no longer supported.

Upstream NEWS:

PostGIS 3.1.0
2020/12/18

This version requires PostgreSQL 9.6 or higher and GEOS 3.6 or higher
Additional features are enabled if you are running GEOS 3.9.

* Breaking changes *
  - #4737, Bump minimum protobuf-c requirement to 1.1.0 (Ra炭l Mar鱈n)
          The configure step will now fail if the requirement isn't
          met or explicitly disabled (--without-protobuf)
  - #4258, Separated postgis_sfcgal from postgis
          into its own lib file and extension (Regina Obe)
  - #4577, Drop support for PostgreSQL 9.5 (Ra炭l Mar鱈n)
  - #4601, ST_TileEnvelope signature changed.
  - #3057, ST_Force3D, ST_Force3DZ, ST_Force3DM and ST_Force4D signatures changed.

* Deprecated signatures *
  - Function postgis_svn_version() replaced by postgis_lib_revision()
    (Sandro Santilli)
  - #4214, Deprecated ST_Count(tablename,...), ST_ApproxCount(tablename, ...)
          ST_SummaryStats(tablename, ..),
          ST_Histogram(tablename, ...), ST_ApproxHistogram(tablename, ...),
          ST_Quantile(tablename, ...), ST_ApproxQuantile(tablename, ...) removed.
          (Darafei Praliaskouski)

* New features*
  - #4687, (GEOS 3.9+) MaximumInscribedCircle (Paul Ramsey)
  - (GEOS 3.9+) Optional gridSize parameter to ST_Union, ST_UnaryUnion,
          ST_Difference, ST_Intersection, ST_SymDifference, ST_Subdivide
          for overlay with exact tolerance (Sandro Santilli)
  - #4624, ST_HexagonGrid and ST_SquareGrid, set returning functions to
          generate tilings of the plane (Paul Ramsey)
  - #4624, ST_Hexagon and ST_Square, shape generators (Paul Ramsey)
  - #4804, (GEOS 3.9+) ST_ReducePrecision allows valid precision reduction
          (Paul Ramsey)
  - #4710, ST_ClusterKMeans now works with 3D geometries (Darafei Praliaskouski)
  - #4801, ST_ClusterKMeans supports weights in POINT[Z]M geometries
          (Darafei Praliaskouski)
  - #4805, _ST_SortableHash exposed to work around parallel soring performance issue
          in Postgres. If your table is huge, use ORDER BY _ST_SortableHash(geom)
          instead of ORDER BY geom to make parallel sort faster (Darafei Praliaskouski)
  - #4625, Correlation statistics now calculated.
          Run ANALYZE for BRIN indexes to start kicking in.
          (Darafei Praliaskouski)
  - #4698, Add a precision parameter to ST_AsEWKT (Ra炭l Mar鱈n)

* Enhancements *
  - #4789, Sped up TopoJSON output for areal TopoGeometry with
          many holes (Sandro Santilli)
  - #4758, Improved topology noding robustness (Sandro Santilli)
  - Make ST_Subdivide interruptable (Sandro Santilli)
  - #4660, Changes in double / coordinate printing (Ra炭l Mar鱈n)
        - Use the shortest representation (enough to guarantee roundtrip).
        - Uses scientific notation for absolute numbers smaller than 1e-8.
          The previous behaviour was to output 0 for absolute values smaller than
          1e-12 and fixed notation for anything bigger than that.
        - Uses scientific notation for absolute numbers greater than 1e+15
          (same behaviour).
        - The precision parameter now also affects the scientific notation
          (before it was fixed [5-8]).
        - All output functions now respect the requested precision (without
          any limits).
        - The default precision is the same (9 for GeoJSON, 15 for everything else).
  - #4746, Micro optimizations to the serialization process (Ra炭l Mar鱈n)
  - #4623, Optimize varlena returning functions (Ra炭l Mar鱈n)
  - #4615, Speed up geojson output (Ra炭l Mar鱈n)
  - #4737, Improve performance and reduce memory usage in ST_AsMVT, especially in
          queries involving parallelism (Ra炭l Mar鱈n)
  - #4719, Fail fast when srids don't match ST_Intersection(geometry,raster)
          Also schema qualify calls in function. (Regina Obe)
  - #4784, Add ST_CollectionExtract(geometry) with default behaviour of
          extracting the components of highest coordinate dimension. (Paul Ramsey)
  - #4675, topology.GetRingEdges now implemented in C (Sandro Santilli)
  - #4672, Cache getSRSbySRID and getSRIDbySRS for better performance (Ra炭l Mar鱈n)
  - #4676, #4657 Avoid decompressing toasted geometries to read only the header
          (Ra炭l Mar鱈n)
  - #4677, Share gserialized objects between different cache types (Ra炭l Mar鱈n)
  - #4601, Add ST_TileEnvelope margin argument (Yuri Astrakhan)
  - #2972, Add quiet mode (-q) to pgsql2shp (Kristian Thy)
  - #3057, Optional value params for Force3D*, Force4D functions (Kristian Thy)
  - #4569, Allow unknown SRID geometry insertion into typmod SRID column (Paul Ramsey)
  - #4149, ST_Simplify(geom, 0) is now O(N).
          ST_Affine (ST_Translate, ST_TransScale, ST_Rotate) optimized.
          ST_SnapToGrid optimized. (Darafei Praliaskouski)
  - #4656, Cast a geojson_text::geometry for implicit GeoJSON ingestion (Ra炭l Mar鱈n)

(gdt)