RkShorten - shorten the reading of the current clause

RkShorten shortens the reading of the current clause.  It does nothing when the reading length is reduced
       to 0.

RkShorten - shorten the reading of the current clause

       This function returns the number of clauses after the change.

                                                                                                    RKSHORTEN(3)

#include<canna/RK.h>intRkShorten(cxnum)intcxnum;