Have the VCL compiler provide a hint about the worst case number of

Have the VCL compiler provide a hint about the worst case number of
operations on the req.hash variable.

It is only a hint, because it merely counts how many times the parser
saw something being added to the req.hash variable.  If the operation
was in a subroutine which was called multiple times, the hint will not
reflect the number of actual operations.

For now we will deal with that at runtime, at the expense of a
failed transaction every time we run short.  If this becomes an issue,
an extensive topological analysis of the VCL program can give us
a definitive count.

git-svn-id: svn+ssh://projects.linpro.no/svn/varnish/trunk@1803 d4fa192b-c00b-0410-8231-f00ffab90ce4