Polish the "securit first" chapter some more
Add a requirement for VCL programs to declare their version like this:

	vcl 4.0;

The first token, after 'include' expansion, has to be such a declaration,
which means that unless the first token in it is 'include' the file
you give to -f, vcl.load or vcl.inline, must start out with "vcl 4.0;"

The point about this is user-support and being able to offer better
backwards compatibility in the future.