[boost] value_cast defect fixed

From: Beman Dawes (beman_at_[hidden])
Date: 1999-08-12 12:25:41

An email from Kevlin Henney caused me to add negative number tests to
cast_test.cpp, and sure enough there was a defect, both in the
implementation and specification.

Both have been fixed.  See http://www.boost.org/libs/utility

Thanks, Kevlin!

--Beman