pgsql: Add: * Allow star join optimizations While our bitmap scan

Log Message:
-----------
Add:

* Allow star join optimizations

  While our bitmap scan allows multiple indexes to be joined to get
  to heap rows, a star joins allows multiple dimension _tables_ to
  be joined to index into a larger main fact table.  The join is
  usually performed by either creating a cartesian product of all
  the dimmension tables and doing a single join on that product or
  using subselects to create bitmaps of each dimmension table match
  and merge the bitmaps to perform the join on the fact table.

Modified Files:
--------------
    pgsql/doc:
        TODO (r1.1730 -> r1.1731)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1730&r2=1.1731)
    pgsql/doc/src/FAQ:
        TODO.html (r1.235 -> r1.236)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.235&r2=1.236)