Introduce refcounted structs for groups of related css properties,
and use them to store the style values. Both GtkCssStaticStyle and
GtkCssAnimatedStyle fill in the structs in GtkCssStyle, and we
can avoid vfuncs for value access, which should be much faster.
We can even start accessing style->core->color directly.
This is just lots of renaming.
The interface remains private, so the public API does not change, apart
from removing the definition of the Interface object to avoid
subclassing.
Instead of keeping an animated style everywhere, we replace it with the
static style when nothing gets animated.
Apart from making the code cleaner, this gets rid of a bunch of animated
style values that do nothing but wrap a static style.
For now, this is only an implementation detail of the animated style.
The idea is to use GtkCssStaticStyle as the result of CSS queries and
then put a GtkCssAnimatedStyle on top that manages the animations. The
neat thing about this is that you can cache the static values.
GtkCssStyle is the base class to be used for all types of styles that do
exist.
GtkCssAnimatedStyle is the only implementation so far, that is exactly a
copy/paste of the old GtkCssStyle code.
