Doc: extend warnings about collation-mismatch hazards in postgres_fdw.

Suppress unnecessary RelabelType nodes in yet more cases.

Prevent drop of tablespaces used by partitioned relations

doc: improve description of synchronous_commit modes

doc: clarify the use of ssh port forwarding

Raise error on concurrent drop of partitioned index

docs: in mapping SQL to C data types, timestamp isn't a pointer

doc: cross-link file-fdw and CSV config log sections

doc: clarify the useful features of procedures

Fix parsing of complex morphs to tsquery

Fix code for re-finding scan position in a multicolumn GIN index.

Fix ALTER TABLE's scheduling rules for AT_AddConstraint subcommands.

Avoid pushing quals down into sub-queries that have grouping sets.