Hajime found that one glyph 'ら' was not rendered correctly in a
vertical Japanese text in examples/texti18n. This was due to an
incorrect calculation of the image sizes.
This change fixes this issue by always adding +1 to the sizes no matter
what the glyph size is or the position is. It is in theory possible to
determine whether this addition is necessary, but this is pretty
complicated and might cause other issues.
