ffutf-specific error codes

Macros
#define	FFUTF_PARSE   1
	Generic UTF parsing error.
#define	FFUTF_EARLY   2
	Parsing finished early (an error).
#define	FFUTF_16LOW   4
	In the UTF-16 string parsed, a high surrogate was found but the lower surrogate was not.
#define	FFUTF_INVAL   8
	UTF codepoint was invalid (not in valid range).
#define	FFUTF_IMPLM   16
	Not implemented.

Detailed Description