SRFI-13/14 merged into guile-core

[Martin Grabmueller]

Hello list,

I have just committed the new directory srfi, including everything
needed to make use of SRFI-13 (string library) and SRFI-14 (character
set library).

I tried to make sure it builds without an installed version of Guile
and installs properly.

The current documentation of the string/character set procedures is in
the file srfi/guile-srfi.texi and I plan to integrate it into part III
of the Reference Manual.

Please let me know if anything breaks.

Regards,
  'martin