- Move utf8_encode and utf8_decode into the strings chapter, since
they were moved out of the XML extension in 7.2
- Recommend mb_convert_encoding, iconv, and UConverter::transcode
when mentioning encoding in passing
- Document UConverter::transcode, based on examination of source
and upstream ICU docs
- Make the language used more consistent, e.g. "convert" rather
than "encode"/"decode", "encoding" rather than "charset"
Closes GH-1418.