Log Message:
Update to 1.999815

Upstream changes:
1.999815 2018-10-19

 * Move bitwise operators signed and, signed or, and signed xor from
   lib/Math/BigInt/CalcEmu.pm into lib/Math/BigInt/Lib.pm. The file
   lib/Math/BigInt/CalcEmu.pm is no longer needed and thus removed.

1.999814 2018-10-01

 * Add to_base() and from_base() to Math::BigInt and corresponding library
   methods _to_base() and _from_base() to Math::BigInt::Lib. This was inspired
   by CPAN RT #122681.

 * Fix Makefile.PL to reflect that Test::More is only needed for testing, not
   for building.

 * In the documentation for each of the to_(bin|hex|oct|bytes) methods, add a
   reference to the corresponding from_(bin|hex|oct|bytes) method.