Handle variable predicates in the generators.

For both SMTLIB and CVC3, variable subtypes conditions are now emitted into
the necessary places.  This doesn't directly relate to the PVS support added
earlier.  For now, no proof is done that the subtype has any allowed input,
but that doesn't matter as the table would still be "valid" for no input.
Determining that the connected Simulink blocks have correct typing is not
considered currently.

git-svn-id: https://groke.mcmaster.ca/svn/grad/colin/branches/TableTool_javization@10855 57e6efec-57d4-0310-aeb1-a6c144bb1a8b