Removed trailing whitespace from all .sml and .sig files.

This affects over 900 files and was done using emacs's delete-trailing-whitespace
function in batch mode. Building the system with Poly/ML and Moscow ML seems to
work, so I'm hoping these changes don't break anything. Please complain if
they do!

Upgraded to build under Kan. 0.

Proper size definitions.

Changes due to the incorporation of John Harrison's datatype definition
package.
Here are the rest of the significant changes. The interface in Datatype
has been fleshed out quite a bit, but what was there has stayed pretty
much the same (except that prim_Hol_datatype doesn't write stuff out
to disk anymore; it's hardly very pure if it does so).

The ind_type theory is the basis for ind_types, which is in turn called
from Datatype.