utf8 cpp library
Release 2.3.1

A bug fix release. Special thanks to dalle and Ivan Sorokin who reported the bugs.

Changes from version 2.3
- Bug fix [3025042]: is_bom documentation issue.
- Bug fix [3083640]: is_code_point_valid incorrectly returns false.
- Bug fix [3167987]: prior moves it before start.
- Bug fix [3185087]: utf8::prior and utf8::previous documentation issue.

Files included in the release: utf8.h, core.h, checked.h, unchecked.h, utf8cpp.html, ReleaseNotes
