Create "Alexandrie-Cairo-Freetype" for cairo code that is only for freetype

[tinchodias]

Cairo doesn't necessarily need the use Freetype API. There is Harfbuzz-Cairo API which could avoid talking to Freetype directly from Alexandrie, to load fonts and render them.

It's not much code for this new package:

• class is AeCairoFreetypeFontFace
• a method extension referencing it (AeFTFace>>#newCairoFontFace)
• check more

[tinchodias]

Additionally, there are FFI bindings to functions that belong to hb-ft.h. In the case we decide to remove those bindings, we could avoid a circular dependency Freetype <-> Harfbuzz. Explained here: harfbuzz/harfbuzz#2524 (comment) (this can be interesting for @tesonep).

There are bindings to functions that begin with hb_tf_:

[tinchodias]

#46 (comment)
is an example of how to totally avoid talking to FreeType directly (we could use it through Harfbuzz).