Fix undersized result buffer in pset_quoted_string().

The malloc request was 1 byte too small for the worst-case output.
This seems relatively unlikely to cause any problems in practice,
as the worst case only occurs if the input string contains no
characters other than single-quote or newline, and even then
malloc alignment padding would probably save the day.  But it's
definitely a bug.

David Rowley

src/bin/psql/command.c

@@ -2711,7 +2711,7 @@ pset_bool_string(bool val)
 static char *
 pset_quoted_string(const char *str)
 {
-	char	   *ret = pg_malloc(strlen(str) * 2 + 2);
+	char	   *ret = pg_malloc(strlen(str) * 2 + 3);
 	char	   *r = ret;
 
 	*r++ = '\'';