range: Remove unused variable
range: Remove unused detail quarks
range: Deprecate detail strings in class struct

... and stop setting them.
range: Simplify defines

- Delete unused defines
- Don't have 2 defines that are multiplied later
scale: Always be flippable

GtkRange only flips horizontal ranges, so there's no need to unset it
for vertical scales.

Also, set_flippable() is a cute name.
range: Remove unused variable
range: Remove 2 variables

Instead, compute their value on-demand.
range: Split out a function

The position of a slider for a given value is something we care a
lot about and jump through hoops to get. See next commit for example.
range: Don't invalidate layout when computing marks

We now have a function to compute a slider position. Use that one
instead.
range: Don't duplicate work

The adjustment value being equal is checked by
gtk_adjustment_set_value() and the necessity of calc_layout() is handled
by the value_changed signal handler.
cssselector: Macroify simple selectors

This is in preparation for the next commits.
cssselector: Add initial support for :not()

:not() works for names, ids, classes and pseudoclasses based on states.

It does not yet work for positional pseudoclasses (like :last-child or
:even) as there is region madness going on with those.
cssselector: Add none selector

We apparently didn't yet parse :not(*), so write a selector for this.
testsuite: Add a bunch of parsing tests for :not()
gtkwidget: Remove unnecessary code in get_state_flags

Any time has_focus is called, we will call gtk_widget_update_state_flags
which will assign the state flags properly.
gtkentry: Pass the correct set of state flags to gtk_style_context_get*

This eliminates a lot of overhead in the CSS engine recalculating
cached CSS rules, and is overall the correct thing to do.
deprecated/gtkstyle: Optimize GtkStyleContext usage

Even though this is deprecated, it's still initialized for every
screen at startup, so let's minimize the cost.
gtkwindow: Optimize GtkStyleContext usage
gtknotebook: Optimize GtkStyleContext usage
gtkcellarea: Optimize GtkStyleContext usage

This is a bit bizarre, but the cell renderer can apply different
flags from the actual style context, and we should use those instead
of the widget flags.