Improving psql slash usage help message

psql slash usage show two options for listing foreign tables.

  \dE[S+] [PATTERN]      list foreign tables
  \det[+] [PATTERN]      list foreign tables

This seems a little odd especially when the output of both of these commands is different.

postgres=# \dE+
           List of relations
 Schema | Name |     Type      | Owner  
--------+------+---------------+--------
 public | foo  | foreign table | highgo
(1 row)

postgres=# \det
  List of foreign tables
 Schema | Table | Server  
--------+-------+---------
 public | foo   | orc_srv
(1 row)


"\dE" displays the list with a "List of relations" heading whereas "\det" displays "List of foreign tables". So, to differentiate the two, I suggest to change the help message for "\dE" to:

  \dE[S+] [PATTERN]      list foreign relations

One could argue that both essentially mean the same thing, however, considering "\dE+" also outputs size, it makes sense IMHO to make this change (as PG documentation: relation is essentially a mathematical term for table). Attached is the patch that makes this change.