More fixes for text rendering

* Fixed missplaced underline with some fonts (including Windows' Arial)
* Fixed glyphs being 2 pixels too large in each dimension because of padding being applied to glyph bounding boxes as well
* Moved underline and strike through a bit so their centre is where it is supposed to be
glyphDesc->advance is actually a vector (noticeable by the .x at the end). If you transform the text through FreeType, then advance will return the true direction vector (in the xy plane) in which the pen position is to be moved. In our case, since we don't transform anything, it will be equal to (horiAdvance, 0). I figured since sf::Font doesn't support rotated glyphs anyway and to better fit the rest of the code, just use the glyph metrics directly :wink:.