[DOCS] Updated documentation in src

[Michael Scott]

I've add inline docs to everything in src (except for malloc.c and 
malloc-trace.c).

At times I wondered whether this was the right thing to do. For 
example, in mmd.c, where Dan had already created a mmd.pod, I ended up 
duplicating information. At other times I reckoned that what was needed 
was an autodoc. Other times the best I could do was rephrase the 
function name. All issues to address in phase 2.

Next I think, for a bit of light relief, I'll do the examples.

For those who want to browse:

	http://homepage.mac.com/michael_scott/Parrot/docs/html/

Mike