master updated (b931e11 -> 418b54e)

[Stefan Kangas]

skangas pushed a change to branch master.

      from  b931e11   Merge from origin/emacs-28
       new  b2bfdd9   Add tests for gif to src/image-tests.el
       new  418b54e   Expand tests for image-type-from-file-header


Summary of changes:
 test/data/image/black.gif | Bin 0 -> 143 bytes
 test/lisp/image-tests.el  |  56 +++++++++++++++++++++++++++++---
 test/src/image-tests.el   |  79 ++++++++++++++++++++++++++++------------------
 3 files changed, 99 insertions(+), 36 deletions(-)
 create mode 100644 test/data/image/black.gif