'int' is enough for 'length' to migrate code from x86 to x64

[FrankLike via Digitalmars-d]

> drop your C.
>
>   auto len = smth.length;
>
> works ok for both x86 and x86_64 (don't know what x64 is).

Many excellent projects such as dfl,dgui,tango, many 'length' 
which type is 'int' or 'uint',they are D's,many people like 
it.but they should migrate to 64 bit.So if 'length' type is 
'int',they can work on 64 bit,but now,they must be modify for 
'length''s type.