Function: tableheight

CALL:

N = tableheight(S)

DESCRIPTION:

Get height (number of rows) of a table.

INPUT:

S any 
<struct> a table structure
flds any 
        optional list of fields, suppresses flds=fieldnames(S). This can
        be usefull if S is not really a table, and one wants to avoi
        tableselect.

OUTPUT
N any 
<integer> height of table