pgsql: Rename pg_stat_file columns to be more consistent.

Log Message:
-----------
Rename pg_stat_file columns to be more consistent.  Split apart change
and creation columns to behave for Unix or Win32.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        func.sgml (r1.280 -> r1.281)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.280&r2=1.281)
    pgsql/src/backend/catalog:
        system_views.sql (r1.20 -> r1.21)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/system_views.sql.diff?r1=1.20&r2=1.21)
    pgsql/src/backend/utils/adt:
        genfile.c (r1.4 -> r1.5)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/genfile.c.diff?r1=1.4&r2=1.5)
    pgsql/src/include/catalog:
        catversion.h (r1.299 -> r1.300)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.299&r2=1.300)