pgsql: Add a new column proiswindow to pg_proc.

Log Message:
-----------
Add a new column proiswindow to pg_proc.  It doesn't actually do anything
useful yet, but I'm tired of re-merging this aspect of the window functions
patch.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        catalogs.sgml (r2.185 -> r2.186)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml?r1=2.185&r2=2.186)
    pgsql/src/backend/catalog:
        pg_proc.c (r1.156 -> r1.157)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_proc.c?r1=1.156&r2=1.157)
    pgsql/src/include/catalog:
        catversion.h (r1.512 -> r1.513)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.512&r2=1.513)
        pg_attribute.h (r1.143 -> r1.144)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_attribute.h?r1=1.143&r2=1.144)
        pg_class.h (r1.109 -> r1.110)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_class.h?r1=1.109&r2=1.110)
        pg_proc.h (r1.532 -> r1.533)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h?r1=1.532&r2=1.533)
    pgsql/src/test/regress/expected:
        opr_sanity.out (r1.87 -> r1.88)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/opr_sanity.out?r1=1.87&r2=1.88)
    pgsql/src/test/regress/sql:
        opr_sanity.sql (r1.71 -> r1.72)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/opr_sanity.sql?r1=1.71&r2=1.72)