Inconsistent/incorrect font sizes with updated nanovg

[jkl1337]

Because the library is using an old version of nanovg there is no support for OpenType fonts and some additional features and numerous rendering fixes that have been updated in stb_truetype.h. However updating nanovg will make all the font sizes and vertical positions wrong in existing themes, widgets and examples. It might be nice to fix this so that sizes are more consistent with the platform.

See:
memononen/nanovg#558
iPlug2/iPlug2#508