#8 CRC-mechanism to avoid double files

[xurux]

=don't include files in an incremental backup if they were
already saved under another name in a previous backup
---

i did program some lines of code, however at the
moment I don't have time to continue;

if someone is also interested in this feature and wants to
continue, he might look at some lines of code i wrote.

i was stuck when i saw that you save an "deleted-
"diskdirentry if a file has been deleted since the last
backup, and don't save an entry if a file still exists and
hasn't been changed. (you probably had in mind that
this saves a bit of disk space for the directory)

also i didn't understand everything how the excludes are
determined and didnt even look at how the restoring is
done.

my idea was to just set a pointer to the older file with
the same content if the crcs match.

the crc-check must only be done if there is a saved file
with a matching size, otherwise the file is saved
immediately.

changes in the source are marked with //*CHANGED*

[xurux]

[pierre]

Logged In: YES
user_id=1110236

Good idea but 2 files with same size & CRC32 does not mean it's the
same content. It's possible to forge CRC32 to have two different files
with the same checksum.