Add RTTI-Support

[Garey27]

Hello, thank you for that awesome script.

I've think its possible to rename RTTI class member functions according to linux one if there same vtable size.

Also i fixed _get_xref_to_calls function:

            func = get_func(xref.frm)
            if (func is None):
                yield xref.to
            else:
                yield func.startEA

I think there was problem xref.to was always same as ea thats why _multiple_xrefs_search was not worked as excepted.

Also maybe rtti renamer function should be rewritted, but im not good at python atm :-)

Here's some results with current implementation on some client dll+so from Half-Life 1:

1. Found 670 (14.7%) functions in total! - no rtti rename
2. Found 1402 (30.8%) functions in total! - rtti vtable size match rename
3. Found 2452 (53.8%) functions in total! - rtti + dirty incorrect vtable size match rename

3 Is looks good but since vtables size mismatch i think in this case we can add some symbol before function like !!CBaseMonster::TraceAttack to indicate that function mb incorrect

RTTI scripts are from: https://github.com/nccgroup/SusanRTTI with little modification to scan vtable functions addresses