src/3rd/tiff: Remove third-party TIFF library

[tuffnatty]

2023-11-12 01:24 UTC+0100 Phil Krylov (phil a t krylov.eu)
  * src/3rd/Makefile
  - src/3rd/tiff/
  * package/harbour.spec
  * README.md
    - Removed third-party TIFF library. It's not clear why it was even included,
      it's not C90 compatible anymore, and a major pain to maintain.

Even @vszakats who added this has removed libtiff in his fork.

[tuffnatty]

This allows non-strict bcc build to finish when using the free non-C99-compliant Borland C++ 5.5 compiler.

[alcz]

C89/90 maintenance burden plus a slight number of CVE security issues...
https://www.cvedetails.com/vulnerability-list/vendor_id-2224/Libtiff.html
libtiff seems to be used by Harbour core developers, it even received patches for WinCE in the past
is it still the case?

[vszakats]

I've added libtiff for convenience in 2012, but Harbour core or contribs never ended up depending on it for anything. Probably very few if anybody is using this. If someone does, it remains (of course) possible to build this outside Harbour. As part of core, it's a maintenance burden, with frequent CVEs, pending bugs, and a local patch to maintain, while making builds longer and more fragile for everybody. I deleted it in 2016.

[tuffnatty]

OK, I am going to merge this.