Bug in method calling with nonconst keys

[Luke Palmer]

There's a pretty bad problem with calling the vtable proxy methods with
keys that aren't constant.  Best illustrated by example:

.sub _main
    newclass $P0, "Foo"
    
    find_type $I0, "Foo"
    new $P1, $I0

    $I1 = $P1["foo"]

    $S0 = "foo"
    $I1 = $P1[$S0]

    end
.end

.namespace ["Foo"]

.sub __get_integer_keyed
    .param pmc key
    print "Key = "
    print key
    print "\n"
    .return(0)
.end

The output is:

Key = foo
Key = 

Thanks,
Luke