Function convert_codepoint_to_unicode_labels 

pub fn convert_codepoint_to_unicode_labels(font: &mut YaffFont)

Convert Codepoint labels to Unicode labels for ASCII range

For all glyphs that don’t have a Unicode label, but do have a Codepoint label, create a Unicode label from the Codepoint label. If there is no encoding, assume ASCII, i.e. convert codepoints 0x20 to 0x7E, ignore the rest. For other encodings, do nothing.