pgsql: Add contrib/pg_freespacemap to display free space map

Log Message:
-----------
Add contrib/pg_freespacemap to display free space map information.

Mark Kirkwood

Modified Files:
--------------
    pgsql/contrib:
        Makefile (r1.61 -> r1.62)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/Makefile.diff?r1=1.61&r2=1.62)
        README (r1.82 -> r1.83)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/README.diff?r1=1.82&r2=1.83)
    pgsql/src/backend/storage/freespace:
        freespace.c (r1.50 -> r1.51)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/freespace/freespace.c.diff?r1=1.50&r2=1.51)
    pgsql/src/include/storage:
        freespace.h (r1.18 -> r1.19)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/freespace.h.diff?r1=1.18&r2=1.19)

Added Files:
-----------
    pgsql/contrib/pg_freespacemap:
        Makefile (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_freespacemap/Makefile?rev=1.1&content-type=text/x-cvsweb-markup)
        README.pg_freespacemap (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_freespacemap/README.pg_freespacemap?rev=1.1&content-type=text/x-cvsweb-markup)
        pg_freespacemap.c (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_freespacemap/pg_freespacemap.c?rev=1.1&content-type=text/x-cvsweb-markup)
        pg_freespacemap.sql.in (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_freespacemap/pg_freespacemap.sql.in?rev=1.1&content-type=text/x-cvsweb-markup)