Fix thinko in plpgsql memory leak fix.

Commit a6b1f5365 intended to place the transient "target" list of
a CALL statement in the function's statement-lifespan context,
but I fat-fingered that and used get_eval_mcontext() instead of
get_stmt_mcontext().  The eval_mcontext belongs to the "simple
expression" infrastructure, which is destroyed at transaction end.
The net effect is that a CALL in a procedure to another procedure
that has OUT or INOUT parameters would fail if the called procedure
did a COMMIT.

Per report from Peter Eisentraut.  Back-patch to v11, like the
prior patch.

Discussion: https://postgr.es/m/f075f7be-c654-9aa8-3ffc-e9214622f02a@enterprisedb.com

src/pl/plpgsql/src/expected/plpgsql_call.out

@@ -152,6 +152,27 @@ CALL test_proc7(100, -1, -1);
  0 | 1
 (1 row)
 
+-- inner COMMIT with output arguments
+CREATE PROCEDURE test_proc7c(x int, INOUT a int, INOUT b numeric)
+LANGUAGE plpgsql
+AS $$
+BEGIN
+  a := x / 10;
+  b := x / 2;
+  COMMIT;
+END;
+$$;
+CREATE PROCEDURE test_proc7cc(_x int)
+LANGUAGE plpgsql
+AS $$
+DECLARE _a int; _b numeric;
+BEGIN
+  CALL test_proc7c(_x, _a, _b);
+  RAISE NOTICE '_x: %,_a: %, _b: %', _x, _a, _b;
+END
+$$;
+CALL test_proc7cc(10);
+NOTICE:  _x: 10,_a: 1, _b: 5
 -- named parameters and defaults
 CREATE PROCEDURE test_proc8a(INOUT a int, INOUT b int)
 LANGUAGE plpgsql

src/pl/plpgsql/src/pl_exec.c

@@ -2235,8 +2235,8 @@ exec_stmt_call(PLpgSQL_execstate *estate, PLpgSQL_stmt_call *stmt)
 			int			i;
 			ListCell   *lc;
 
-			/* Use eval_mcontext for any cruft accumulated here */
-			oldcontext = MemoryContextSwitchTo(get_eval_mcontext(estate));
+			/* Use stmt_mcontext for any cruft accumulated here */
+			oldcontext = MemoryContextSwitchTo(get_stmt_mcontext(estate));
 
 			/*
 			 * Get the parsed CallStmt, and look up the called procedure

src/pl/plpgsql/src/sql/plpgsql_call.sql

@@ -141,6 +141,30 @@ $$;
 
 CALL test_proc7(100, -1, -1);
 
+-- inner COMMIT with output arguments
+
+CREATE PROCEDURE test_proc7c(x int, INOUT a int, INOUT b numeric)
+LANGUAGE plpgsql
+AS $$
+BEGIN
+  a := x / 10;
+  b := x / 2;
+  COMMIT;
+END;
+$$;
+
+CREATE PROCEDURE test_proc7cc(_x int)
+LANGUAGE plpgsql
+AS $$
+DECLARE _a int; _b numeric;
+BEGIN
+  CALL test_proc7c(_x, _a, _b);
+  RAISE NOTICE '_x: %,_a: %, _b: %', _x, _a, _b;
+END
+$$;
+
+CALL test_proc7cc(10);
+
 
 -- named parameters and defaults