splitting up cf.data.pre in the CVS repository

This has been discussed a couple of times before, but there was no final
conclusion, so lets try again.

I propose storing cf.data.pre split in one file per directive in the CVS
repository, as generated by the scripts/split-cf.data.pre.pl

The purpose is to ease maintenance when merging squid.conf documentation
cross releases or branches, and avoiding massive changes when
reorderingthe directives.

Unless someone opposes to this change I'll do it next friday.

Regards
Henrik