BUG #12963: WHERE constraints on (INNER) JOIN columns are not propagated to both tables

The following bug has been logged on the website:

Bug reference:      12963
Logged by:          Gian-Carlo Pascutto
Email address:      gcp@sjeng.org
PostgreSQL version: 9.4.1
Operating system:   Linux
Description:

The relevant parts of the schema are as follows:

CREATE TABLE matches
(
  seq integer NOT NULL,
  start_time integer NOT NULL,
  <blah>
  CONSTRAINT matches_pkey PRIMARY KEY (seq)
)

CREATE TABLE matches_players
(
  seq integer NOT NULL,
  player_num smallint NOT NULL,
  account_id integer,
  <blah>
  CONSTRAINT matches_players_pkey PRIMARY KEY (seq, player_num),
  CONSTRAINT matches_players_seq_fkey FOREIGN KEY (seq)
      REFERENCES matches (seq) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION
)

The following is the EXPLAIN ANALYZE output of 2 queries.
https://dl.dropboxusercontent.com/u/32496746/postgresql.txt

Because this is an (INNER) JOIN, a WHERE constraint that is given to one
table, on the joined column, applies to the other table as well.
PostgreSQL's query planner does not understand this and consequently
produces a query plan that is a factor 35 slower than when one restates the
constraint.

That is, when given:

        join matches on matches.seq = matches_players.seq
        where matches.seq > 1151575404 and matches.seq < 1155066769

there should be no need to add:

        and matches_players.seq > 1151575404 and matches_players.seq <
1155066769;

because this is implied by the JOIN ON.