Sort out paired double quotes in \connect, \password and \crosstabview.

In arguments, these meta-commands wrongly treated each pair as closing
the double quoted string.  Make the behavior match the documentation.
This is a compatibility break, but I more expect to find software with
untested reliance on the documented behavior than software reliant on
today's behavior.  Back-patch to 9.1 (all supported versions).

Reviewed by Tom Lane and Peter Eisentraut.

Security: CVE-2016-5424

src/bin/psql/psqlscanslash.l

@@ -671,6 +671,7 @@ dequote_downcase_identifier(char *str, bool downcase, int encoding)
 				/* Keep the first quote, remove the second */
 				cp++;
 			}
+			else
 				inquotes = !inquotes;
 			/* Collapse out quote at *cp */
 			memmove(cp, cp + 1, strlen(cp));

src/test/regress/expected/psql_crosstab.out

@@ -46,15 +46,15 @@ SELECT v, to_char(d, 'Mon') AS "month name", EXTRACT(month FROM d) AS num,
 (3 rows)
 
 -- ordered months in vertical header, ordered years in horizontal header
-SELECT EXTRACT(year FROM d) AS year, to_char(d,'Mon') AS "month name",
+SELECT EXTRACT(year FROM d) AS year, to_char(d,'Mon') AS """month"" name",
   EXTRACT(month FROM d) AS month,
   format('sum=%s avg=%s', sum(i), avg(i)::numeric(2,1))
   FROM ctv_data
   GROUP BY EXTRACT(year FROM d), to_char(d,'Mon'), EXTRACT(month FROM d)
 ORDER BY month
-\crosstabview "month name" year format year
- month name |      2014       |      2015      
-------------+-----------------+----------------
+\crosstabview """month"" name" year format year
+ "month" name |      2014       |      2015      
+--------------+-----------------+----------------
  Jan          |                 | sum=3 avg=3.0
  Apr          |                 | sum=10 avg=5.0
  Jul          | sum=5 avg=5.0   | sum=4 avg=4.0

src/test/regress/sql/psql_crosstab.sql

@@ -29,13 +29,13 @@ SELECT v, to_char(d, 'Mon') AS "month name", EXTRACT(month FROM d) AS num,
  \crosstabview v "month name" 4 num
 
 -- ordered months in vertical header, ordered years in horizontal header
-SELECT EXTRACT(year FROM d) AS year, to_char(d,'Mon') AS "month name",
+SELECT EXTRACT(year FROM d) AS year, to_char(d,'Mon') AS """month"" name",
   EXTRACT(month FROM d) AS month,
   format('sum=%s avg=%s', sum(i), avg(i)::numeric(2,1))
   FROM ctv_data
   GROUP BY EXTRACT(year FROM d), to_char(d,'Mon'), EXTRACT(month FROM d)
 ORDER BY month
-\crosstabview "month name" year format year
+\crosstabview """month"" name" year format year
 
 -- combine contents vertically into the same cell (V/H duplicates)
 SELECT v, h, string_agg(c, E'\n') FROM ctv_data GROUP BY v, h ORDER BY 1,2,3