Further improvement

* Mix of HPDF_WMODE_HORIZONTAL and HPDF_WMODE_VERTICAL in starting and
relief fonts.
* Vertical alignment options of HPDF_Page_TextRect (Improvement of
Davyjones' ideas).
* Interlinear annotation by IAA (interlinear annotation anchor, U+FFF9),
IAS (interlinear annotation separator, U+FFFA), IAT (interlinear
annotation terminator, U+FFFB) embedded in text.