Add then add support for prefix unary operations.

Now add the actual prefix unary operation support.  For now, just deal with
negation (~), and cheat the code gen appropriately.  But for the future,
things are ready for use.

git-svn-id: https://groke.mcmaster.ca/svn/grad/colin/branches/TableTool_javization@10469 57e6efec-57d4-0310-aeb1-a6c144bb1a8b