[PATCH] remove squid-old.h

Hi all,
  the attached (huge) bundle builds upon Amos' recently compat work,
and removes squid-old.h, reconnecting the wires as needed
Secondary objectives are:
- sort included files in many places (first squid in alphabetical
order, then squid conditionally included, then system).
- change some SQUIDCEXTERN into c++-linkage extern

It passes a full test-suite on my kubuntu; it should be in a decent
shape for merging.
Can you give it a check? In case you need, the branch is at
lp:~kinkie/squid/sourceformat

Thanks

-- 
    /kinkie