Updates for the documentation subtree.

Illustrate some not-so-common programming techniques.
Improve hello-world
More links between different sections.


git-svn-id: svn://svn.code.sf.net/p/amforth/code/trunk@1536 fd1c0b69-5d68-47f5-910c-86182ebb6ecd
Merge branch 'hq'