s11n: easy object serialization in C++

File Release Notes and Changelog

Release Name: 1.2.4

Notes:
Please see the changelog.

Changes:

1.2.4:

Only minor touch-ups. If 1.2.3 works for you, there is no need to
upgrade.

- Corrected install path for user manual: PREFIX/share/... instead of
  PREFIX/shared/...

- Corrected install process to honor ${DESTDIR}.

- Updated the "nobuildfiles" Makefile to build a shared lib. Only works
  with g++. Also added very basic [un]install rules.

- Commented out the name of an unused parameter in some traits code,
  to avoid a warning from gcc4.

- Fixed a missing ::std:: in the <s11n.net/s11n/proxy/std/multimap.hpp>