Fix ofTrueTypeFont

fixes a bug in `ofTrueTypeFont::getStringAsPoints(...)` when using strings with "strange" characters. 
there are a lot of diffs as I just moved parts of the code up and down to make it easier to spot the bug, yet the only real changes are within `ofTrueTypeFont::getStringAsPoints(...)` and `ofTrueTypeFont::getCharactersAsPoints(...)`
related to issue https://github.com/openframeworks/openFrameworks/issues/1848