xml2: Fix failure with xslt_process() under -fsanitize=undefined

Fix misuse of "volatile" in xml.c

xml2: Improve error handling of libxml2 calls

Improve error handling of libxml2 calls in xml.c

Improve the names generated for indexes on expressions.

Use SnapshotDirty when checking for conflicting index names.

Make libpq_pipeline.c shorter and more uniform via helper functions.

Allow resetting unknown custom GUCs with reserved prefixes.

Obtain required table lock during cross-table constraint updates.

Fix some new issues with planning of PlaceHolderVars.

Remove planner's have_dangerous_phv() join-order restriction.

Revert support for improved tracking of nested queries

psql: Forbid use of COPY and \copy while in a pipeline

psql: Abort connection when using \syncpipeline after COPY TO/FROM

pg_restore: Fix wrong descriptions of --with-{schema,data,statistics} options.