Improvements around Unicode and other

Improvements around Unicode:
* Unicode supplement planes support.
* UTF-16/UTF-32 support.
* New UTF encodings.

Improvements around font:
* CID text and ToUnicode map for not only UTF-8 but also all of
CMapEncoders.
* TrueType font loading options to sellect CID text and ToUnicode map.
* Text converter for UTF encodings.
** UTF character encoding converter.
** User defined converter.
** Built-in converter "BiDi" for right-to-left languages such as Arabic,
using GNU FriBiDi.
* Relief font for CID/TrueType font.

Improvements of HPDF_Page_TextRect:
* Hyphenation by SHY (soft hyphen, U+00AD) embedded in text.
* Line break by ZWSP (zero width space, U+200B) embedded in text.
* Kanji justification.
* HPDF_TALIGN_JUSTIFY adjusts not only char-space but also word-space
and Arabic kashida.
* Kashida by ARABIC TATWEEL (U+0640) embedded in text, using "BiDi"
converter.
* HPDF_WMODE_VERTICAL support