GLib 2.62 deprecated GTimeVal and GTime because they are not Y2038-safe.
Since we expose these types in our public API, we need to disable
warnings to avoid projects breaking horribly just by importing
gdk-pixbuf.h.

Sadly, GdkPixbufAnimation public types not only require GTimeVal in
virtual function signatures for loaders, but they also do not have any
room left in the class vtable for adding int64 variants.