Add support for building with waf

* Add a git-submodule 'rtems_waf' that points to the git
  repository located at http://git.rtems.org/chrisj/rtems_waf.git
* Add a wscript

TODO:
* Bring in CFLAGS / other !common options
* Make the executable actually work (looks like it's missing the tarfile,
  or rather it is not getting built correctly)
modified tar file generation to use file and directory names rather than '.'