Import new 2-clause BSD licenced implementation of the bc and dc commands

These implementations of the bc and dc programs offer a number of advantages
compared to the current implementations in the FreeBSD base system:

• They do not depend on external large number functions (i.e. no dependency on OpenSSL or any other large number library)

• They implements all features found in GNU bc/dc (with the exception of the forking of sub-processes, which the author of this version considers as a security issue).

• They are significantly faster than the current code in base (more than 2 orders of magnitude in some of my tests, e.g. for 12345^100000).

• They should be fully compatible with all features and the behavior of the current implementations in FreeBSD (not formally verified).

• They support POSIX message catalogs and come with localized messages in Chinese, Dutch, English, French, German, Japanese, Polish, Portugueze, and Russian.

• They offer very detailed man-pages that provide far more information than the current ones.

Approved by: imp
Obtained from: https://git.yzena.com/gavin/bc
Differential Revision: https://reviews.freebsd.org/D19982