[vtk] Avoid stdext::checked_array_iterator.

[Oleg2]

Fixes #51766.

What this fixes

VTK's bundled (pre-7.0) copy of fmtlib at ThirdParty/diy2/vtkdiy2/include/vtkdiy2/fmt/format.h references stdext::checked_array_iterator under #ifdef _SECURE_SCL. This extension has been removed from the MSVC standard library in MSVC 14.51 (VS 2026 Preview), so the build fails with:

error C2653: 'stdext': is not a class or namespace name
error C2061: syntax error: identifier 'checked_array_iterator'

(full failure log in #51766)

Resolution

Drop the _SECURE_SCL branch and keep only the raw-pointer fallback. The patched make_checked / checked_ptr aliases become unconditional pass-throughs. This is the same approach already accepted in vcpkg for the same removal across five other ports:

PR	Port
#51750	cpprestsdk
#51774	breakpad
#51749	duckdb
#51753	ampl-mp
#51785	luminoengine

Files

• ports/vtk/diy2-fmt-remove-stdext-checked-array-iterator.patch — the source patch
• ports/vtk/portfile.cmake — register the patch
• ports/vtk/vcpkg.json — port-version 15 → 16
• versions/v-/vtk.json, versions/baseline.json — version DB bump (via vcpkg x-add-version vtk)

Local verification

Built vtk[core]:x64-windows against this overlay port using MSVC 14.51.36231 (VS 2026 Preview, generator Visual Studio 18 2026). The failing vtkDIYDataExchanger.cxx translation unit now compiles cleanly.

Manifest

• Changes comply with the maintainer guide.
• SHA512s are updated for each updated download. (no source changes)
• The "supports" clause reflects platforms that may be built. (unchanged)
• Any fixed CI baseline entries are removed from that file. (none applicable)
• Any patches that are no longer applied are deleted from the port's directory. (none)
• The version database is fixed by rerunning ./vcpkg x-add-version --all and committing the result.
• Only one version is added to each modified port's versions file.

[Oleg2]

Withdrawing — switching to a local-only patch in my private vcpkg checkout. The patch (ports/vtk/diy2-fmt-remove-stdext-checked-array-iterator.patch) and its construction notes remain available in the commit if anyone wants to revive it as their own PR.

[BillyONeal]

Is there something wrong with it? (Why withdraw it? Would rather give you credit for the fix if it actually fixes)

To be clear I have not reviewed, I just saw linked to my other PR