Test cases for bug in Interval.unary_- and Interal.*(rhs: A) with rhs < 0, the bug appearing when the interval is unbounded from one side.
Bugfix in Interval.unary_* and Interval.*(rhs: A).
Merge pull request #259 from denisrosset/master

Bugfix in Interval.unary_- and Interval.*(rhs: A) when intervals are half-unbounded.