(Re-)assign code points to the fi and fi ligature characters

[dpk]

PyFontaine insists that fi and fl be given the Unicode values U+FB01 and U+FB02, respectively, for Adobe Latin 1 support. Also those codepoints (whatever we think of them and whether they should exist) don’t work, at least on the Mac, without this explicit assignment.

This should be simple but needs doing in all font files:

• [x] Roman
• [x] Italic
• [x] Semibold
• [x] Bold
• [x] Display Italic