Use pgSphere 1.5.2 and improve ADQL 2.1

[kimakan]

This PR aligns ADQL translation with ADQL 2.1 and updates the PostgreSQL backend for pgSphere 1.5.2. The ADQL translator requires pgSphere 1.5.2 from postgrespro/pgsphere and its PostGIS dependency.

• Align ADQL parsing with 2.1, including quoted identifiers, NULL values,
  expressions, and mandatory math functions.
• Use native pgSphere geometry types without fork-specific array serializers:
  POINT(10, 20) becomes spoint(RADIANS(10), RADIANS(20)), while stored
  pgSphere columns remain unchanged.
• Translate ADQL distance predicates efficiently:
  DISTANCE(stored_spoint, POINT(...)) <= 2.5 becomes
  spoint_dwithin(stored_spoint, spoint(...), RADIANS(2.5)).

[coveralls]

coverage: 95.47% (-0.4%) from 95.869% — 0.8.0dev0 into master