pgsql: psql: Add \gx command

psql: Add \gx command

It can often be useful to use expanded mode output (\x) for just a
single query. Introduce a \gx which acts exactly like \g except that it
will force expanded output mode for that one \gx call. This is simpler
than having to use \x as a toggle and also means that the user doesn't
have to worry about the current state of the expanded variable, or
resetting it later, to ensure a given query is always returned in
expanded mode.

Primairly Christoph's patch, though I did tweak the documentation and help
text a bit, and re-indented the tab completion section.

Author: Christoph Berg
Reviewed By: Daniel Verite
Discussion: https://postgr.es/m/20170127132737.6skslelaf4txs6iw%40msg.credativ.de

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/b2678efd43f17db7dfa04e0ca076ea01275cd9bc

Modified Files
--------------
doc/src/sgml/ref/psql-ref.sgml | 12 ++++++++++++
src/bin/psql/command.c | 9 +++++++--
src/bin/psql/common.c | 7 +++++++
src/bin/psql/help.c | 1 +
src/bin/psql/settings.h | 1 +
src/bin/psql/tab-complete.c | 11 ++++++-----
src/test/regress/expected/psql.out | 23 +++++++++++++++++++++++
src/test/regress/sql/psql.sql | 7 +++++++
8 files changed, 64 insertions(+), 7 deletions(-)