/*
 *  call-seq:
 *     Dvector.min_of_many(ary)  ->  number or nil
 *
 *  Returns the minimum value held in the array of Dvectors (or <code>nil</code> if _ary_ is empty).
 *  Any +nil+ entries in _ary_ are ignored.
 *  
 */ 
VALUE dvector_min_of_many(VALUE klass, VALUE ary) {