Make error handling when painting fonts less strict
Ticket #472 reports Chars choking on the font AsanaMath. This doesn't appear to be a bug, more a zealous response to an error when trying to paint characters within the font - currently, Chars switches to the System Font whenever it encounters a problem.
The proposed change relaxes this a bit, skipping anything that Font_Paint or Font_ScanString errors, but warning the user. Discussion of these changes is here: https://www.riscosopen.org/forum/forums/3/topics/15163. The font is also attached as a zip file.
Does this look like a sensible change?