pgsql: Remove trailing whitespace from *.sgml files.

Remove trailing whitespace from *.sgml files.

Historically we've been lax about this, but seeing that we're not
lax in C files, there doesn't seem to be a good reason to be so
in the documentation. Remove the existing occurrences (mostly
though not entirely in copied-n-pasted psql output), and modify
.gitattributes so that "git diff --check" will warn about future
cases.

While at it, add *.pm to the set of extensions .gitattributes
knows about, and remove some obsolete entries for files that
we don't have in the tree anymore.

Per followup discussion of commit 5a892c9b1.

Discussion: https://postgr.es/m/E1nfcV1-000kOR-E5@gemulon.postgresql.org

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/836af9756b742f5a8ae77b4bef9d27311772a13c

Modified Files
--------------
.gitattributes | 7 +--
doc/src/sgml/advanced.sgml | 8 +--
doc/src/sgml/backup.sgml | 2 +-
doc/src/sgml/bloom.sgml | 8 +--
doc/src/sgml/charset.sgml | 12 ++--
doc/src/sgml/datatype.sgml | 32 +++++------
doc/src/sgml/dblink.sgml | 6 +-
doc/src/sgml/ddl.sgml | 4 +-
doc/src/sgml/fdwhandler.sgml | 2 +-
doc/src/sgml/func.sgml | 92 ++++++++++++++---------------
doc/src/sgml/high-availability.sgml | 2 +-
doc/src/sgml/hstore.sgml | 8 +--
doc/src/sgml/json.sgml | 6 +-
doc/src/sgml/logical-replication.sgml | 58 +++++++++----------
doc/src/sgml/logicaldecoding.sgml | 26 ++++-----
doc/src/sgml/monitoring.sgml | 2 +-
doc/src/sgml/pageinspect.sgml | 26 ++++-----
doc/src/sgml/parallel.sgml | 2 +-
doc/src/sgml/perform.sgml | 4 +-
doc/src/sgml/pgfreespacemap.sgml | 4 +-
doc/src/sgml/pgstatstatements.sgml | 4 +-
doc/src/sgml/pgsurgery.sgml | 10 ++--
doc/src/sgml/pgwalinspect.sgml | 6 +-
doc/src/sgml/planstats.sgml | 14 ++---
doc/src/sgml/plperl.sgml | 2 +-
doc/src/sgml/plpgsql.sgml | 4 +-
doc/src/sgml/postgres-fdw.sgml | 6 +-
doc/src/sgml/ref/create_index.sgml | 4 +-
doc/src/sgml/ref/explain.sgml | 4 +-
doc/src/sgml/ref/pgarchivecleanup.sgml | 3 +-
doc/src/sgml/ref/pgtestfsync.sgml | 2 +-
doc/src/sgml/ref/psql-ref.sgml | 14 ++---
doc/src/sgml/ref/reindex.sgml | 4 +-
doc/src/sgml/ref/rollback_to.sgml | 4 +-
doc/src/sgml/ref/select.sgml | 2 +-
doc/src/sgml/ref/set_role.sgml | 4 +-
doc/src/sgml/ref/set_session_auth.sgml | 4 +-
doc/src/sgml/ref/show.sgml | 2 +-
doc/src/sgml/release-15.sgml | 4 +-
doc/src/sgml/rules.sgml | 8 +--
doc/src/sgml/syntax.sgml | 14 ++---
doc/src/sgml/test-decoding.sgml | 2 +-
doc/src/sgml/textsearch.sgml | 102 ++++++++++++++++-----------------
doc/src/sgml/xaggr.sgml | 4 +-
doc/src/sgml/xfunc.sgml | 16 +++---
45 files changed, 275 insertions(+), 279 deletions(-)