pgsql: Change array comparison rules to consider dimensionality

Log Message:
-----------
Change array comparison rules to consider dimensionality information,
not only the array contents, before claiming two arrays are equal.
Per recent discussion.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        func.sgml (r1.294 -> r1.295)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.294&r2=1.295)
    pgsql/src/backend/utils/adt:
        arrayfuncs.c (r1.124 -> r1.125)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/arrayfuncs.c.diff?r1=1.124&r2=1.125)