Log Message:
libheif: update to 1.18.0.

now reads images generated by iOS 18
heif-convert has been renamed to heif-dec
encoding: property item boxes with identical content are reused
experimental codec plugins for VVC (vvenc/vvdec and uvg266)
experimental codec plugin for OpenJPH (High-throughput JPEG2000)
support ISO 23001-17 version 1 uncC minimized headers
support ISO 23001-17 images with 'deflate', 'zlib' and Brotli compression
heif-enc can read TIFF images
API functions to read/write raw items and item properties
many bug fixes and smaller enhancements