Some little changes I did to support Gforth 0.7.9

The migration from Gforth 0.7.3 to 0.7.9 broke most of my programs, but
it was easy to solve.

For example, many of my programs used the undocumented string operator
`s+`, which, as the repository shows, was removed years ago. I simply
added it to my personal library.

Also, in Gforth 0.7.3 `basename`, `dirname`, and `scan-back` were
defined in `forth-wordlist`, but in Gforth 0.7.9 they are defined in the
`c-lib` vocabulary. I added them to my personal library, simply as
synonyms in `forth-wordlist`, to make them accessible as before.

No problem. Just wanted to share.

-- 
Marcos Cruz
http://programandala.net