All "Simple Fonts" in PDF (all but Type0 fonts) have the property that
glyphs are selected with single byte character codes. This means that
the Encoding objects should use u8 for representing these character
codes. Moreover, and as mentioned in a previous commit, there is no need
to store the unicode code point associated with a character (which was
in turn wrongly associated to a glyph).
This commit greatly simplifies the Encoding class. Namely it:
* Removes the unnecessary CharDescriptor class.
* Changes the internal maps to be u8 -> FlyString and vice-versa,
effectively providing two-way lookups.
* Adds a new method to set a two-way u8 -> FlyString mapping and uses
it in all possible places.
* Simplified the creation of Encoding objects.
* Changes how the WinAnsi special treatment for bullet points is
implemented.
286e3e6872