Port "move pixelate filter to gd_filter.c" (sync with upstream)

[cmb69]

Cf. libgd/libgd@0f0894a.

[nielsdos]

Is the goal to completely sync all upstream fixes into bundled libgd? How do you approach this?

[cmb69]

Is the goal to completely sync all upstream fixes into bundled libgd?

My goal is to finally unbundle libgd (this is long overdue; the double maintenance is a nightmare). Since this can't happen right away (one show-stopper are missing custom allocators; in my opinion particularly important for image reading), I'm trying to pave the way to get both in sync (without too much BC breaks in one version; I don't see unbundling or complete sync as realistic option for PHP 8.5).

Note that this is not one-way, though. There are some cases where our bundled libgd seems to be correct, but not external (e.g. libgd/libgd#928).

How do you approach this?

Pretty much ad-hoc. Doing some diffs, ignoring minor differences (such as formatting and comments), focusing on relevant differences. And not to step on my toes with too many conflicting PRs. :)

[nielsdos]

I see. Note that there is some PHP-specific code in the bundled (search for e.g. VCWD) so they might not reach equivalence easily.

[cmb69]

Note that there is some PHP-specific code in the bundled (search for e.g. VCWD) so they might not reach equivalence easily.

Yeah, but at least some of that is broken anyway (see https://bugs.php.net/64823).