Update the definition and operations of rtti_varmaps ...

... as a first step to addressing Mantis bug #585.

compiler/hlds_rtti.m:
    Give more descriptive names to

    - the types of the four fields of the rtti_varmaps type,
    - the names of those fields,
    - the variables that represent values of those fields, and
    - the predicates that operate on the values of those fields.

    Put the fields dealing with typeclasses next to each other.

    Add XXXs where warranted.

    Add an experimental attempt to address Mantis bug #585.

compiler/simplify_proc.m:
    Add code to report the problem that causes Mantis bug #585.
    Disable it, until we fix the issue with
    tests/typeclasses/extra_typeinfo.m.

compiler/handle_options.m:
    Note a problem with how we handle the implications of typeinfo liveness.

    Delete a duplicate comment.

tests/invalid/tci_liveness_abort.{m,err_exp}:
tests/invalid/Mercury.options:
tests/invalid/Mmakefile:
    Add and enable the test case for Mantis bug #585. We do not
    pass it yet, because passing it would screw up the next test case.

tests/typeclasses/extra_typeinfo.{m,exp}:
    Print the values of three variables on three lines, not one.

    Fix misleading code.