SECURITY UPDATE: use-after-free through stale zstream pointers
debian/patches/CVE-2026-46675.patch: add png_inflate_detach_buffers
to clear the zstream input and output pointers and counters, and
call it on claim in png_inflate_claim and on release in
png_decompress_chunk, png_handle_iCCP and png_read_finish_IDAT
(pngrutil.c), so that png_read_end called before row reading no
longer inflates through a stale next_in into a freed buffer