Add basic support for ZapfDingbats

This patch adds support for the `ZapfDingbats` encoding, and should thus fix issues/bugs with titles like: "check&nbsp;marks rendered as a number (4)".

Compared to the rendering in Adobe Reader, many of the glyphs doesn't look as nice. However, it should still be a *marked* improvement compared to the current situation where we don't even attempt to draw the correct glyphs.

/cc @yurydelendik