Fix mosml's basis2002 emulation to include full ListPair module.

This will fix the recent Moscow ML build failures.

Code for the new basis2002 functions is mainly taken from the as-yet
unreleased Moscow ML 2.10, but I have made foldrEq tail-recursive.

Allow Moscow ML build to happen using (as yet unreleased) v2.10.

Basic strategy is to make adoption of basis 2002 even more
thorough. In particular, the Timer structure is now as per
the 2002 Basis.

It is possible to detect that one is working with Moscow ML 2.10 or
later by checking the Holmakefile variable $(HAVE_BASIS2002), which is
set (to value "1") when in 2.10 or later. It is unset elsewhere. See
an example of its use in help/src-sml/Holmakefile.

Make OS.FileSys.fullPath fail if the path doesn't exist.

This is in line with what is specified in the 2002 Basis.

Fix: Basis 2002 calls for Option exception to be present at top-level.

Put Math structure inside structure Real in Basis2002.

More changes to get basis2002 changes working properly in both poly + mosml.

Implement more of Basis2002 for Moscow ML (adding Vector, Array,
ArraySlice and VectorSlice), simplifying what Poly/ML has to emulate.
Haven't done full rebuild test, but have got as far as integerTheory
and Omega, which makes heavy uses of Vector etc.

Fix for the basis2002.sml implementation of Word8Vector.
(The error made its vector type independent of the existing vector,
rather than a synonym as intended.)

Update us to use the Basis2002 version of Word8Vector. Seems to
affect only src/parse/CharSet.sml. (Changes to tools/configure.sml
make it better at detecting situations where basis2002.{uo,ui} need to
be transferred to sigobj.)

Make the basis hack for Moscow ML correctly identify which version of
the Basis Library we are trying to emulate.