pgsql: Fix contrib/hstore to throw an error for keys or values that

Log Message:
-----------
Fix contrib/hstore to throw an error for keys or values that don't fit in its
data structure, rather than silently truncating them.  Andrew Gierth

Modified Files:
--------------
    pgsql/contrib/hstore:
        hstore.h (r1.6 -> r1.7)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/hstore/hstore.h?r1=1.6&r2=1.7)
        hstore_io.c (r1.8 -> r1.9)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/hstore/hstore_io.c?r1=1.8&r2=1.9)
        hstore_op.c (r1.11 -> r1.12)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/hstore/hstore_op.c?r1=1.11&r2=1.12)
    pgsql/doc/src/sgml:
        hstore.sgml (r1.2 -> r1.3)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/hstore.sgml?r1=1.2&r2=1.3)