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.
Fixes a couple bugs...
- Pixel font sizes in css would render as point sizes.
- For em font sizes, where the parent size was set and not default, we would
incorrectly convert a pixel value from points to pixels.
We'll always grab the default font size in pixels so we don't keep confusing
things.
Worth noting that gtk css font-size will still behave differently than the
web. Pango interprets font-size differently.
This requires adding code to do math on number values:
gtk_css_number_value_multiply()
and
gtk_css_number_value_try_add()
were added to achieve that.
Some tests are included.
GtkCssNumberValue is now a base class for numbers.
Actual numbers are now implemented in GtkCssDimensionValue. The name is
borrowed from the CSS spec, so there.
