vcs: Remove all mention of use of -ve revision numbering. The introduction seems forced. It's a neat trick, but doesn't fit into the flow of things. Now introducing revision numbering with the need to take diffs between particular commits. Also mention -v and -l parameters to the log command.

Richard Stallman%http://www.stallman.org
Eric Raymond%http://www.catb.org/~esr/
Ian Murdock%http://ianmurdock.com/
Lawrence Lessig%http://lessig.org
Linus Torvalds%http://torvalds-family.blogspot.com/
Guido van Rossum%http://www.python.org/~guido/
Larry Wall%http://www.wall.org/~larry/