hstore-new - hstore-new: deal with strictness/null issues.

Log Message:
-----------
deal with strictness/null issues. support nulls when creating from
records and arrays (both useful and consistent with the => operator).
regression tests for null handling.

Modified Files:
--------------
    hstore-new:
        hstore-new.sql.in (r1.2 -> r1.3)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/hstore-new/hstore-new/hstore-new.sql.in?r1=1.2&r2=1.3)
        hstore_io.c (r1.3 -> r1.4)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/hstore-new/hstore-new/hstore_io.c?r1=1.3&r2=1.4)
    hstore-new/expected:
        hstore.out (r1.1.1.1 -> r1.2)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/hstore-new/hstore-new/expected/hstore.out?r1=1.1.1.1&r2=1.2)
    hstore-new/sql:
        hstore.sql (r1.1.1.1 -> r1.2)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/hstore-new/hstore-new/sql/hstore.sql?r1=1.1.1.1&r2=1.2)