Log Message:
Add shells/guile-gash version 0.1

Gash is a POSIX-compatible shell written in Guile Scheme.  It provides
both the shell interface, as well as a Guile library for parsing shell
scripts.  Gash is designed to bootstrap Bash as part of the Guix
bootstrap process. There are plans to develop Gash into a
general-purpose shell and tool for building interfaces between Scheme
and the shell.

Features of the shell
* Sophisticated enough to be used to build Bash.
* Has a nice colorized prompt.
* Includes all of the POSIX-specified "special" built-ins except for
  `times'.
* Includes about half of the POSIX-specified "regular" built-ins
  (see `gash/built-ins.scm' for details).

Features of the programming interface
* Parses Shell scripts into an AST.
* Provides a rudimentary interface for writing Shell-like Scheme
  scripts.