[Linux] fixed font rendering artifacts, added simple line break

This patch fixed the size calculations for true type fonts (especially for
italic fonts)
Additinally a very simple greedy line break algorithm has been added for
true type labels.
Merge pull request #2167 from Weeds/feature-linux-fontdimensions

fixed #1834: [Linux] fixed font rendering artifacts, added simple line break.
This patch fixed the size calculations for true type fonts (especially for
italic fonts)
Additinally a very simple greedy line break algorithm has been added for
true type labels.