Yay, works!

Not hooked up to hb-ot-font yet.

We're not going to define public macros for tags for tables.
There's little use to those and they are implementation detail.

Untested!

The 'avar' table does not allow random access to axis maps,
so change API to avoid quadratic-time implementation.

Removed -hb_ot_var_normalize_axis_value(), added
+hb_ot_var_normalize_variations() and
+hb_ot_var_normalize_coords() instead.

Hopefully also fixes build failure on msvc.

hb-view correctly renders variations with ft font-funcs now.
hb-ot-font needs HVAR implementation.

Is hooked up to the font, but not to FreeType, so raster doesn't show yet.

Documentation needs to be done.

Looks much better.

Supports enumerating variation axes, normalizing values, etc.