Pure Perl module to test Math::BigInt with scalars

Changes for 2.002000 - 2023-12-02

• Fix bug in Math::BigFloat method bsin(). It can now handle any argument to any precision. Also improve downgrading. This fixes CPAN RT #150590 and the bsin() part of CPAN RT #107604.
• Fix bug in Math::BigFloat method bexp(). Specifying precision (rather than accuracy) used to give a NaN. Also improve downgrading.
• Improve upgrading in Math::BigInt methods bsin() and bcos(). They now upgrade only when necessary.