Fix #9659.

BUnicodeChar::ToUTF8() had the same regression as ::FromUTF8() as far as
not advancing the input string pointer, which broke building
case-insensitive queries.

src/kits/locale/UnicodeChar.cpp

@@ -245,6 +245,7 @@ BUnicodeChar::ToUTF8(uint32 c, char **out)
 {
 	int i = 0;
 	U8_APPEND_UNSAFE(*out, i, c);
+	*out += i;
 }