GNU Forth interpreter that is ANSI compliant.

NOTE: If you Compile or otherwise install the Ffcall package, GForth
will also have the ability to call libraries of C software. Ffcall
must be installed first in order for GForth to detect this, however.
However, GForth can run on its own without Ffcall. For this reason,
Ffcall is not listed as a dependency.
