Issue #2332295 by sanduhrs, klausi, er.pushpinderrana, Berdir | jfha73: Fixed Unicode requirements check not working with PHP 5.6.

Issue #1317628 by Albert Volkman, Gaelan, disasm, mjonesdinero, xjm: Clean up API docs for include files n-z

Issue #1446372 by Heine, bserem, champlin: Fixed Invalid Unicode code range in PREG_CLASS_UNICODE_WORD_BOUNDARY fails with PCRE 8.30.

#1007486 by mlncn: Fixed Documentation problem with truncate_utf8: refers to max_return_length instead of max_length

- Patch #878408 by pwolanin, Damien Tournoud: replace decode_entities() with built-in html_entity_decode().

- Patch #855988 by pwolanin, Damien Tournoud, David_Rothstein: get rid of preg_replace() with /e in decode_entities().

- Patch #768040 by jhodgdon, janusman, codycraven: truncate_utf8() only works for latin languages and drupal_substr() had a bug.

- Patch #352359 by Damien Tournoud: provided unit tests for the unicode library and fixed some bugs.

- Patch #64967 by Arancaytar, meba: ereg -> preg for performance reasons and future compatilbility.  PHP6 is rumoured to drop ereg support.

- Patch #245115 by kkaefer, John Morahan, JohnAlbin et al: after a long discussion we've decided to make the concatenation operator consistent with the other operators.

#200185 by Pancho: truncate_utf8() was abused as if it was an UTF-8 character based string function, so align our code to that. Can be renamed to drupal_truncate_chars() in Drupal 7.

#184867 by deekayen, catch and keith.smith: fix some spelling errors in our source code and messages printed

See: http://drupal.org/node/64279#t-placeholders