Commit 5e4e248 added a mp_image_params field to mp_image, and moved many
parameters to that struct. display_w/h was left redundant with
mp_image_params.d_w/d_h. These fields were supposed to be always in
sync, but it seems some code forgot to do this correctly, such as
vf_fix_img_params() or mp_image_copy_attributes(). This led to the
problem in github issue #756, because display_w/_h could become
incorrect.
It turns out that most code didn't use the old fields anyway. Just
remove them. Note that mp_image_params.d_w/d_h are supposed to be always
valid, so the additional checks for 0 shouldn't be needed. Remove these
checks as well.
Fixes#756.
f6f8dc7782