This solves Bug#72: LargeInteger.valueOf(java.math.BigInteger.valueOf(-1)) is "-0".
The problem is that in LargeInteger.valueOf(bytes,offset,length) the _size is
incorrectly set to 0 in this case. My fix for that is to include the line
if (isNegative && wordIndex < 0) wordIndex = 0; // special case for -1
li._size = wordIndex + 1;
Caution: I don't understand the code completely and this is probably not the
most elegant fix. It seems to work though - my unittests verify this works with
a number of values.