set idle_in_transaction_session_timeout to 0

statement_timeout is being set to 0 in session preventing failures
when this parameter is non-zero. This change is to prevent failures due
to idle-in-transaction timeout, which look like this:

```
FATAL:  terminating connection due to idle-in-transaction timeout
ERROR: query failed: server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
DETAIL: query was: SAVEPOINT repack_sp1
```

bin/pg_repack.c

@@ -487,11 +487,12 @@ preliminary_checks(char *errbuf, size_t errsize){
 	}
 
 	/* Query the extension version. Exit if no match */
-	res = execute_elevel("select repack.version(), repack.version_sql()",
+	res = execute_elevel("select repack.version(), repack.version_sql(), current_setting('server_version_num')::int >= 90600",
 		0, NULL, DEBUG2);
 	if (PQresultStatus(res) == PGRES_TUPLES_OK)
 	{
 		const char	   *libver;
+		const char	   *has_iitst;
 		char			buf[64];
 
 		/* the string is something like "pg_repack 1.1.7" */
@@ -518,6 +519,13 @@ preliminary_checks(char *errbuf, size_t errsize){
 					buf, libver);
 			goto cleanup;
 		}
+
+		/* If Postgres version is 9.6 or newer, disable idle-in-transaction timeout */
+		has_iitst = getstr(res, 0, 2);
+		if (0 == strcmp("t", has_iitst))
+		{
+			command("SET idle_in_transaction_session_timeout = 0", 0, NULL);
+		}
 	}
 	else
 	{
@@ -1703,6 +1711,10 @@ lock_access_share(PGconn *conn, Oid relid, const char *target_name)
 
 	termStringInfo(&sql);
 	pgut_command(conn, "RESET statement_timeout", 0, NULL);
+	if (PQserverVersion(conn) >= 90600)
+	{
+		pgut_command(conn, "RESET idle_in_transaction_session_timeout", 0, NULL);
+	}
 	return ret;
 }
 

regress/expected/nosuper.out

@@ -14,6 +14,6 @@ ERROR: pg_repack failed with error: You must be a superuser to use pg_repack
 -- => ERROR
 \! pg_repack --dbname=contrib_regression --table=tbl_cluster --username=nosuper --no-superuser-check
 ERROR: pg_repack failed with error: ERROR:  permission denied for schema repack
-LINE 1: select repack.version(), repack.version_sql()
+LINE 1: select repack.version(), repack.version_sql(), current_setti...
                ^
 DROP ROLE IF EXISTS nosuper;

regress/expected/nosuper_1.out

@@ -14,4 +14,6 @@ ERROR: pg_repack failed with error: You must be a superuser to use pg_repack
 -- => ERROR
 \! pg_repack --dbname=contrib_regression --table=tbl_cluster --username=nosuper --no-superuser-check
 ERROR: pg_repack failed with error: ERROR:  permission denied for schema repack
+LINE 1: select repack.version(), repack.version_sql(), current_setting('server_version_num')::int >= 90600
+               ^
 DROP ROLE IF EXISTS nosuper;