Refactor to use iterators
Use Plane::row() and PlaneSlice::row()
Test Plane::iter()
Add PlaneSlice::row()
Add Plane::row()
Do not use Plane::p() to dump the images
CI: Update nasm to 2.15.05
Move render size validation to Config::validate()
Assert that render_size is non-zero in both dimensions
Detect invalid use of enable_timing_info with still_picture
Assert that render_size fits in 32 bits