D2 phobos BigInt bug

[ZHOU Zhenyu]

BigInt b = "100000";
foreach( i; 1..20 ){
    b*=10;
    writeln(b*b);
}

system: Windows
CPU: Intel Core2 Duo T7250 2.00GHz
result:
1000000000000
100000000000000
10000000000000000
1000000000000000000
100000000000000000000
10000000000000000000000
999981553255926290448384
100000000000000000000000000
10000000000000000000000000000
1000000000000000000000000000000
100000000000000000000000000000000
10000000000000000000000000000000000
1000000000000000000000000000000000000
100000000000000000000000000000000000000
10000000000000000000000000000000000000000
999999999999999999999981553255926290448384
100000000000000000000000000000000000000000000
9999999999999999999999999981553255926290448384
1000000000000000000000000000000000000000000000000