Minimal Scheme Implementation for use as an Extension Language

Chibi-Scheme is a very small library intended for use as an extension
and scripting language in C programs. In addition to support for
lightweight VM-based threads, each VM itself runs in an isolated heap
allowing multiple VMs to run simultaneously in different OS threads.

The default repl language contains all bindings from R7RS small,
available explicitly as the (scheme small) library. The language is
built in layers, however - see the manual for instructions on compiling
with fewer features or requesting a smaller language on startup.

Chibi-Scheme is known to work on 32 and 64-bit Linux, FreeBSD and OS X,
Plan 9, Windows (using Cygwin), iOS, Android, ARM and Emscripten.
