Fonts with the encoding name "WinAnsiEncoding" should render missing
characters above character code 040 (octal) as a "bullet" character.
This patch adds Encoding::should_map_to_bullet(char_code) which is then
called by char_code_to_code_point() to check if the given char code
should be displayed as a bullet instead.
I didn't have a good way to test this, so I've only verified that it
works by manually overriding inputs to the function during the rendering
stage.
This takes care of a FIXME in the Annex D part of the PDF specification.
d6a3be1615