src/num/theories/SingleStep.{sig,sml} is gone. The
defininitions of Cases, Cases_on, Induct, Induct_on,
CASE_TAC (and co.) are now in basicProof/BasicProvers.
completeInduct_on and measureInduct_on are now in
numLib. recInduct is now in src/tfl/Induction.sml.
All these are collected in bossLib, so the changes
should be invisible to ordinary users.

SingleStep.*.doc has been changed accordingly.

BasicProvers.NORM_TAC should now automatically perform
all case splits (from if-then-else expressions as
well as case expression) arising anywhere in the goal.

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!

Fixed so that induction theorems are as general as possible. Previously,
tupled arguments in function definitions would lead to tuples of variables
in the consequent of the induction theorem. This was needlessly specific.
Some proofs will break (i.e., become shorter) as a result.

Upgraded tflLib to Kan.0.

Kananaskis compatibility.

Ongoing revisions. Defn has been split into a basic datastructure
and manipulations (Defn0) and the definition entrypoints (Defn).
This allows a prettyprinter for the "defn" type to be automatically
installed when the std.prelude runs. Defn0 is part of basicHol90.

Big re-organizational changes. Tfl and tflLib are gone ... the relevant
files are instead Defn and TotalDefn.