boron: Add devel/boron version 2.1.0

Boron is an interpreted, prototype-based, scripting language similar to Rebol.
The interpreter and datatype system is a C library useful for building
domain-specific languages (DSLs) embedded in C/C++ applications.

It is a smaller language than Rebol with fewer built-in data types, no infix
operators, and no built-in internet protocols.  It does add the capability to
slice series values and store data in a serialized binary format.