Added test cases for #437 and #438.

These test cases are related to character range of expressions, which
are currently not well supported.
WyC: Fix for #392.

This fixes a problem when accidentally compiling a file kind is
effectively unknown.  Previously, a null pointer message was reported.
WyIL: Changes to first part for #435.

This change partly completes the updating of the WyIL bytecode to
support multiple requires/ensures clauses.  The purpose of this is to
enable better error reporting for individual ensures clauses.
WyIL: Bug fix for #435.

There was a problem related to the construction of postconditions and
their input variables.
WyIL: working on figuring last few bugs for #435.
WyIL: Attempting to resolve problems for #435.

Specifically, there is some bug which is causing two tests to fail.  The
bug appears to be related to a block which is imported in
RuntimeAssertions representing the precondition of an invocation.  For
some reason, the inputs for this precondition are set wrong, or
something is somehow going wrong.
WyIL: Fixed bug in WyiFileWriter #435.

The WyilFileWriter was not correctly writing out the number of pre- or
post-condition blocks when there was more than one.
WyC: Bug fix for precondition generation #435.

There was a minor bug in the way that preconditions were being
generated.  This was causing issues during verification.
WyC: Bug fix for Postcondition Generation #435

This is a bug which is confirmed to have existed before, but somehow got
through.  I'm not quite sure how!
WyC: Yet another bug fix for #435; related to #436.

This is yet another bug fix related to the incorrect normalisation of
type invariants for inclusion into postconditions.  The problem is
related to the fact that a type invariant has only one input, whereas a
postcondition has at least as many inputs as there are parameters.
WyC: Uncommented tests which now pass.

A number of verification tests now pass as a result of the previous bug
fix.  I have now gone through and uncommented these.  There were about 9
of them, and could be others since I didn't try them all.