pgsql: Add pg_column_size() to return storage size of a column,

Log Message:
-----------
Add pg_column_size() to return storage size of a column, including
possible compression.

Mark Kirkwood

Modified Files:
--------------
    pgsql/doc/src/sgml:
        func.sgml (r1.262 -> r1.263)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.262&r2=1.263)
    pgsql/src/backend/access/heap:
        tuptoaster.c (r1.49 -> r1.50)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/heap/tuptoaster.c.diff?r1=1.49&r2=1.50)
    pgsql/src/backend/utils/adt:
        varlena.c (r1.124 -> r1.125)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/varlena.c.diff?r1=1.124&r2=1.125)
    pgsql/src/include/access:
        tuptoaster.h (r1.22 -> r1.23)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/access/tuptoaster.h.diff?r1=1.22&r2=1.23)
    pgsql/src/include/catalog:
        pg_proc.h (r1.373 -> r1.374)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h.diff?r1=1.373&r2=1.374)
    pgsql/src/include/utils:
        builtins.h (r1.258 -> r1.259)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/builtins.h.diff?r1=1.258&r2=1.259)