CairoFontEngine: improve type3 font rendering
This is my attempt at rebasing !1183 with conflicts fixed, as it's been two weeks since !1183 (comment 1784449)
My C++ skills are really, really limited, so I hope that I did not mess anything up. I did test this change for quite a while and works without issues. There also one comment regarding has_color
that I am not sure if still applies after the changes in master.
Closes !1183
Fixes #1337 (closed)