note vector fix in changelog

remove mention of exr save in configure

oops

update for newer pandoc

"smart" extension is no longer supported for docbook

bump version for animated webp load fix

allow spng.pc and libspng.ps for libspng discovery

note HEIC fix in changelog

see libvips#1921

fix build with libheif save buit not load

We had some definitions inside the #ifdef HEIFLOAD.

Thanks estepnv

libvips#1844

note render thread change in changelog

fix write ICC profile to webp

ooops, a typo broke ICC profile write to webp 18 days ago

thanks augustocdias

see libvips#1767

Merge pull request libvips#1756 from libvips/heif-workaround

try to work around some broken heic images