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

Merge branch 'master' of github.com:libvips/libvips

add LT_INIT

remove mode_t from headers

it seems to fail with MSVC.

int works fine, and is what g_open() uses.

thumbnail could fail on HEIC in some modes

in locked UP or DOWN mode, vips_thumbnail() could incorrectly select the
thumbnail from a HEIC image even when it was not large enough to
generate the output image.

Thanks ZorinArsenij

See libvips#1614

lock for metadata changes

Another attempt at fixing crashes on metadata chenage in highly threaded
applications.

Global lock around set, remove and copy metadata. This is crude, but
simple, the performance impact should be small, and ought to resolve the
problem.

We'll do something better for the next version.

see lovell/sharp#1986

fix some autorot issues

and a problem with vipsthumbnail of tif

see libvips#1515