make arrayjoin much faster with large arrays

arrayjoin was making a region on every input image during startup, and
repeating for each thread (!!) so large arrays could be very expensive
to join.

Instead, make input regions on demand, and computre set of required
input images rather than searching for them.

See libvips#3247

note release date for 8.14

Ensure EXIF is at least 4 bytes before inspection (libvips#3109)

spngsave: name ICC profiles (libvips#3068)

The PNG spec requires that the iCCP chunk has a profile name with
a minumum length of 1 (we use the same "icc" name as pngsave).

dzsave: improve compatibility with libgsf < 1.14.29 (libvips#3017)

* Implement `GsfOutfileStdio` by ourselves

* Add missing `->root` init

* Fix styling

* Update ChangeLog

Link the main library with `-Wl,-z,nodelete` to prevent unloading (li…

…bvips#2934)

See: libvips/php-vips-ext#44

Meson: remove redundant `--no-undefined` link argument (libvips#2918)

This is already controlled by the `b_lundef` built-in option, which defaults to `true`.

fix "make dist" ready for 8.13 rc1

note pipe read fix in changelog

note jp2k load just in changelog