pgsql: Convert hash join code to use MinimalTuple format in tuple hash

Log Message:
-----------
Convert hash join code to use MinimalTuple format in tuple hash table
and batch files.  Should reduce memory and I/O demands for such joins.

Modified Files:
--------------
    pgsql/src/backend/executor:
        execTuples.c (r1.95 -> r1.96)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execTuples.c.diff?r1=1.95&r2=1.96)
        nodeHash.c (r1.103 -> r1.104)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeHash.c.diff?r1=1.103&r2=1.104)
        nodeHashjoin.c (r1.82 -> r1.83)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeHashjoin.c.diff?r1=1.82&r2=1.83)
    pgsql/src/include/executor:
        hashjoin.h (r1.38 -> r1.39)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/executor/hashjoin.h.diff?r1=1.38&r2=1.39)
        nodeHash.h (r1.40 -> r1.41)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/executor/nodeHash.h.diff?r1=1.40&r2=1.41)
        nodeHashjoin.h (r1.32 -> r1.33)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/executor/nodeHashjoin.h.diff?r1=1.32&r2=1.33)
        tuptable.h (r1.32 -> r1.33)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/executor/tuptable.h.diff?r1=1.32&r2=1.33)