Cut0

The 0-cut ];.0 (also [)
on vector and matrix right arguments is now implemented by special code,
resulting in time/space savings. For example:

   v=: 1e4$'asdf'
   ] p=: ?.2##v
1315 7556
   m=: ?111 97$1e6
   ] q=: ?. 2 2$$m
14 73
50 51
   ts=: 6!:2 , 7!:2@]