Improve documentation of FT_BBox.
Improve documentation of FT_BBox.

xlgames-inc/XLE,yorung/XLE,xlgames-inc/XLE,yorung/XLE,yorung/XLE,xlgames-inc/XLE,xlgames-inc/XLE,xlgames-inc/XLE,yorung/XLE,yorung/XLE,xlgames-inc/XLE,xlgames-inc/XLE,xlgames-inc/XLE,yorung/XLE,yorung/XLE,yorung/XLE