Avoid rounding error in image rotation

* src/image.c (image_set_rotation): Halve translations as double values.
1 job for master in 53 minutes and 6 seconds
Status Job ID Name Coverage
  Test
failed #2240
test-all

00:53:06

 
Name Stage Failure
failed
test-all Test
Makefile:318: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
make[1]: *** [check-expensive] Error 2
Makefile:293: recipe for target 'check-expensive' failed
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:957: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1