Issue clearer notice when inherited merged columns are moved

CREATE TABLE INHERIT moves user-specified columns to the location of the
inherited column.

Report by Fatal Majid
Document use of partial indexes for partial unique constraints

Report by Tomáš Greif

Backpatch through 9.4
Update URL reference material in /contrib/isn docs

Report by Peter Eisentraut
Allow \watch to display query execution time if \timing is enabled.

Previously \watch could not display the query execution time even
when \timing was enabled because it used PSQLexec instead of
SendQuery and that function didn't support \timing. This patch
introduces PSQLexecWatch and changes \watch so as to use it, instead.
PSQLexecWatch is the function to run the query, print its results and
display how long it took (only when \timing is enabled).

This patch also changes --echo-hidden so that it doesn't print
the query that \watch executes. Since \watch cannot execute
backslash command queries, they should not be printed even
when --echo-hidden is set.

Patch by me, review by Heikki Linnakangas and Michael Paquier
Update comment to reflect commit 1d41739e5a04b0e93304d24d864b6bfa3efc45f2.

Peter Geoghegan
Fix segmentation fault that an empty prepared statement could cause.

Back-patch to all supported branches.

Per bug #11335 from Haruka Takatsuka
doc: Remove dead link

The link to the NIST web page about DES standards leads to nowhere, and
according to archive.org has been forwarded to an unrelated page for
many years.  Therefore, just remove that link.  More up to date
information can be found via Wikipedia, for example.
Add tab-completion for reloptions like user_catalog_table.

Back-patch to 9.4 where user_catalog_table was added.

Review by Michael Paquier
Assorted message fixes and improvements