Finish testing fixed point support for CVC3.

Fixed point operations are now all tested.  Due to literals automatically
casting to reals, it is necessary to push the "x" variable further into the
expression.  To ensure everything works, add one more condition without x to
make sure everything stays stable.  Everything works, after adjusting search
strings.

Also, deal with both signed/unsigned fixed point types.

git-svn-id: https://groke.mcmaster.ca/svn/grad/colin/branches/TableTool_javization@10711 57e6efec-57d4-0310-aeb1-a6c144bb1a8b