Skips to the next character in a UTF-8 string.
The string must be valid; this macro is as fast as possible, and has no error-checking.
You would use this macro to iterate over a string character by character.
The macro returns the start of the next UTF-8 character.
Before using this macro, use
g_utf8_validate() to validate strings
that may contain invalid UTF-8.
This function is not directly available to language bindings.