package/postgis: new package

package/postgis: new package

PostGIS is a spatial database extender for PostgreSQL object-relational
database. It adds support for geographic objects allowing location
queries to be run in SQL.

On microblazeel with the bootlin toolchain, the build fails with an ICE:

  during RTL pass: reload
  .../bootlin-microblazeel-uclibc/build/libgeos-3.9.0/src/geom/util/Densifier.cpp: In static member function ‘static std::unique_ptr<std::vector<geos::geom::Coordinate> > geos::geom::util::Densifier::densifyPoints(geos::geom::Coordinate::Vect, double, const geos::geom::PrecisionModel*)’:
  .../bootlin-microblazeel-uclibc/build/libgeos-3.9.0/src/geom/util/Densifier.cpp:128:1: internal compiler error: in gen_reg_rtx, at emit-rtl.c:1155
  128 | }
      | ^

Since it's unlikely that postgis will ever be used on a microblaze,
simply disable it.

https://postgis.net/

Signed-off-by: Maxim Kochetkov <fido_max@inbox.ru>
Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Reviewed-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
[Arnout:
 - Move postgresql dependency to package/Config.in, to satisfy
   alphabetical ordering in the menu while keeping it below postgresql.
 - Add dependency on !microblaze.
 - Add comment for dependencies.
 - Add positive version of --with-raster and --with-protobuf to
   _CONF_OPTS.
 - Expand BSD to BSD-2-Clause.
]