kron() with hypermats: new algo 10x faster

kron() with hypermats: new algo 10x faster

 test_run ast kron
 test_run elementary_functions bug_13339

a = rand(4,4);
b = rand(500,500,4);
tic()
r1 = a .*. b;
disp(toc())
tic();
r2 = newKron(a,b);
disp(toc());
disp(and(r1==r2))

--> exec('test_10464.sce', -1)
   63.77736
   5.2832192   = 12.1 x faster
  T

With
a = rand(40,40,2);
b = rand(25,25,4);
// I get
   18.998866
   1.7675572  = 10.7x faster

Change-Id: I6344b7aa0d55bbedcb0a53bfab18dfcfb9b9a80e