VARIANT / parameter handling

[maul-esel]

Related to #5.

Change the way parameters are handled so they don't need to be explicitly typed. Instead, use ITypeInfo to retrieve the expected VT.

Concept:

id = ITypeInfo->GetIDsOfNames(name)
index = ITypeInfo2->GetFuncIndexOfMemId(id)
func = ITypeInfo->GetFuncDesc(index)
for (i = 0; i < func->cParams; i++)
{
    vt = func->lprgelemdescParam[i]->tdesc->vt
    VariantChangeType(var, var, vt)
}
ITypeInfo->ReleaseFuncDesc(func)

Also check out how AHK does this internally.