Extract function slurp_image from image loading

* src/image.c (slurp_image): New function...
(xbm_load, xpm_load, pbm_load, webp_load, svg_load): ...extracted from
here.
2 jobs for master in 43 minutes and 50 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Build Images
failed #75076
build-image-inotify

00:43:50

 
  Normal
skipped #75077
test-src-inotify
 
Name Stage Failure
failed
build-image-inotify Build Images
net/http: request canceled (Client.Timeout exceeded while awaiting headers)
Running after_script
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
$ find ${test_name} ! \( -name "*.log" -o -name ${EMACS_TEST_JUNIT_REPORT} \) -type f -delete
find: build-image-inotify-bf4d4ab4: No such file or directory
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1