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!

The help wasn't building under PolyML due to a (possible) PolyML bug. This
works around the problem.

Make this directory build Moscow ML versions of the help executables,
promoting Scott's PolyML version of Database to be the primary
version. In general, take the attitude that PolyML sources here can
be primary, and that the Moscow ML stuff can be made to work with
appropriate use of My* structures, and Holmakefile magic.
When this is confirmed to work (really just need to test makebase),
I will remove help/src entirely.

Got the help build system working on PolyML.

Start working on porting the doc building system to SML (i.e., not Moscow ML)
to get it working with Poly ML.