Refactorized convert(byte[], int, ...), now uses the pointer version.
Refactorized Convert(char[], int, ...) to use the pointer version.
Implemented method 'IsUnknownSurrogate()'.
removed index check because (1) it cannot be checked in this context and (2) it
only explains when a bad sequence started in the current or past buffer (in
this case it would take a negative value).
removed index check because (1) it cannot be checked in this context and (2) it
only explains when a bad sequence started in the current or past buffer (in
this case it would take a negative value).